The most powerful moments in The Time Of The Doctor didn't involve a stand-off against intergalactic bullies and mad despots - they involved the Doctor reflecting on his time, and slowly giving in to the ravages of age. In this vein, Smith managed to wring genuine emotion out of his final on-screen appearance, but also nailed the quieter moments: the shutdown of a disembodied cyber-head is also the loss of a trusted friend.

(It) is a celebration of the recent past, and a dedication to the Eleventh Doctor, and his time in the Tardis. Time marches on for everybody, even Doctor Who, and everything eventually ends. While there is comfort in the fact that the story goes on, the Eleventh Doctor's time is over. It might have been silly sometimes, and the time-travel shenanigans often got overly complicated, but it was another fine chapter in the lives and times of Doctor Who. The next one is about to begin, but there is plenty of fun and emotion in the Eleventh's chapter that is worth celebrating.

I shed a tear in the knowledge that possibly the best Doctor the show has seen in its half century is no more. Smith had the ability to persuade his audience that he was, indeed, a millennium old man in a very young man's body. Well, on Boxing Day night on Prime, he discarded that body like a favourite suit too worn and raggedy to patch anymore. RIP 11. We are already missing you.

Smith is at his glorious best in this special, with plenty of reminders of why he might just be the best Doctor yet. Scrub that, he is the best yet and I'm going to miss his portrayal terribly.

The episode is ripe with writer/producer Steven Moffat's leitmotifs: messages sent across space and time, gatherings of The Doctor's rivals, small towns and sheriff badges. And some of the show's classic tropes: broken technology, the TARDIS telephone and lots of lovely one-liners. The risk, of course, is that the episode is so laden with in-universe references and nods to past episodes, moments, characters and aliens than it becomes almost impossible to navigate for someone without even a cursory knowledge of Doctor Who lore.

This is a pensive finish, but not gut-wrenching in the way that Davies wrote previous Doctor David Tennant's farewell. This is gentler, with only a cameo from his beloved Amy Pond (Karen Gillan) who says goodbye to her "raggedy man". Even Smith's lovely scene with old-school Fourth Doctor Tim Baker in the anniversary special was richer, and more touching. (And tearful, for Baker-era fans anyway.)

But salvation comes in the form of a gift, once promised (but never delivered) by the Time Lords to The Master in the 20th anniversary special The Five Doctors: a new life cycle of twelve regenerations. Which means that Peter Capaldi's Doctor becomes not the Twelfth Doctor, as previously thought, but the First Doctor, beginning a new chapter of life for the universe's most beloved Time Lord. And the comfortable assurance that his hope, his strength and, best of all, his eccentric madness, remains a light which will never be extinguished.

Even though the date of Smith's leaving and the identity of his successor, Peter Capaldi, had been known for some time, watching the episode knowing it was Smith's last kept at least one American viewer anxious and sad, with a finger on the pause button for when things got too heavy. Possibly there are still viewers, avid viewers even, who have never quite cottoned to him — Tennant continues to cast a long shadow — but I have loved his work. Elegant and heartfelt, authoritative and playful, swashbuckling and intimate, alien and familiar, Smith's acting has accommodated and, as it were, humanized every oddball, paradoxical, high-concept, low-humor passage Moffat has thrown at him.

It was always going to be so when facing the long-standing question of regeneration limits. Precedent for more regenerations being granted had been established before, and Steven Moffat led just about enough crumbs to the key moment to deal with the issue, without dwelling too much on it. Job done, whether you like the way it was done or not.

The Time Of The Doctor, then, brought the curtain down on what has to be classed as a successful 50th anniversary year for Doctor Who, that's had its bumps, but also given us some absolute treats. The Time Of The Doctor in itself is unlikely to go down as one of the Who highlights of 2013 in truth. We quite enjoyed it, but it still felt a bit underwhelming. Still, Smith's performance as the Doctor is undoubtedly one of the year's highlights, and it's very clear that the show is going to miss him a lot. What's also clear is that there are further exciting times ahead.

The lead writer achieves many things in this 2013 Christmas special: tying up straggly ends from Matt’s era – why the Tardis exploded in 2010, why Silence must fall, the big question that must never be answered… Points that most viewers have long since forgotten. The attentive fan is being serviced here.

Lots of ticks for advancing the legend of our hero and giving him a new lease of life. You can’t blame Moffat for taking on the responsibility – and allowing himself the honour in this golden anniversary year – of dealing with the “12 regenerations only” issue, which has dogged Doctor Who since it was established in The Deadly Assassin (1977). The future looks assured.

So farewell, fair Doctor! After 44 episodes spread across four years, magnificent Matt Smith discards his bowtie and lets it drop, poignantly, to the floor of the Tardis. And – after a rather protracted regeneration – in pounces Peter Capaldi. Gaunt, lizard-like and with frou-frou hair. Was anyone else put in mind of Doctor Pretorius from Bride of Frankenstein? I doubt Capaldi will portray his Doctor as a venomous dowager (unlike Ernest Thesiger in that 1935 black comedy) but I live in hope of a degree of archness.

let’s not forget Smith: he gave a cracking final performance before bowing out. He even managed to convincingly portray a wizened old Doctor. While David Tennant’s departure from the role of the Doctor was drenched in saccharine, self-referential sentimentality, there was very little of that in Smith’s final adventure. There were little nods to the 11th Doctor’s adventures and even a surprise guest appearance from Karen Gillan, who played his companion Amy Pond, but the nostalgia was reserved for Christmas.

Overall, as Doctor Who Christmas specials go, The Time of the Doctor was a sci-fi spectacular: there was time travel, spaceships and plenty of villains for the Doctor to face, including Daleks, Cybermen and Weeping Angels.

While some aspects of the story may have been lost on the casual viewer, it was nevertheless an adventure the whole family could enjoy.

Smith has been so good as the ageless, sinister, childlike, loveable alien that it was almost a shame to see that expressive Easter Island head caked in make-up for the middle section of this episode, while the swelling strings and Shakespearian speechifying of the final quarter-hour seemed comically at odds with the intricate lunacy that animates his best performances.

But there were some genuinely funny gags, Peter Capaldi looks promisingly demented in the role, Orla Brady was truly superb as a sexy spacefaring nun and the whole thing went off with as much of a bang for Smith as it could plausibly have done. I remain confused on a main plot point — if the return of the Time Lords would have started a war, why does no one bat an eyelid when the Doctor slaughters a planetful of Daleks with golden energy? But no doubt that, like so much else, has already been pitchforked laughingly into Later.

It was perhaps the most Christmassy Christmas special they've ever pulled off. I'm sure Doctor Who has thrilled me more in the past. It's certainly blindsided me more. And it may well have made me cry more, although it feels difficult to imagine such a moment right now. But I'm certain it's never managed to do all three so successfully at once. Merry Christmas. I hope we can all be there for each other at this difficult time.

The new (twelfth? First?) Doctor's arrival was quick and explosive. We didn't even get a changing-faces scene, which felt like an appropriate tease. But dear lord, he certainly looks like he's going to be angry. Should we wonder whether this new First Doctor is going to be based on the other First Doctor? Or are they doing a new, and hopefully better, version of the Sixth Doctor's violent, unstable regeneration?

This year's thoughtful Doctor Who managed to combine an 800th episode with a regeneration, then tied it all up with a Christmas Day bow. For his final episode, the BBC really got their money's worth out of Matt Smith, who carried much of the Time of the Doctor alone, and it was a neat trick to show the youngest ever Doctor getting old. Steven Moffat ticked all necessary boxes here: he answered the regeneration question (though it made little sense to this non-devotee) and gave incoming timelord Peter Capaldi a suitably sizable entrance: "Do you happen to know how you fly this thing?"

Easily the highlight of this year’s Christmas viewing, The Time of the Doctor not only gave Matt Smith a great send off but also gave viewers a careful, concise and emotional hour of top-quality entertainment. And as is typical for Who, renewal and regeneration are only the start of a brand new adventure, and from his brief introduction (“Kidneys!”) Peter Capaldi looks like a fine successor to take the world’s favourite TV hero in a different and equally exciting direction.

"The Time of the Doctor" was, if I'm being honest, kind of a let down as Matt Smith's final episode. It felt like it dragged a bit in the middle, and I never really cared about the town of Christmas or the Doctor being its savior for several hundred years. To be fair, I've been building this episode up in my mind for months, and it had to follow the well-received "The Day of the Doctor." It would have been nearly impossible for the episode to live up to expectations. There were aspects that I enjoyed however. The truth field was a nice touch, because the Doctor has never been a truthful man. He's skated by on lies and half-truths and being the smartest person in the room, so it was interesting to watch him simply have to stay quiet after several seasons of being a wound-up chatterbox.

Matt Smith's Doctor will forever be remembered for his eccentricities, for successfully filling the very large shoes of David Tennant, for his inability to talk without flapping his arms about, and for his love of fish fingers and custard, bowties and fezzes. But the most important aspect of his tenure was his relationship with Amy Pond, the first face Eleven ever encountered, and it's unfortunate that Smith's swan song was nearly devoid of any real emotion until the final few moments when she returned to say good night as he regenerated into Capaldi's Doctor.