Now I have to disagree slightly with Magnus. The episode wasn't the greatest, I'll fully concede that point, but it was far from a throwaway. 11's departure was a reflection of his arrival. All of the iconic imagery from 11's time was slowly stripped away. fish fingers and Custard (still, ew) Amy/Amelia, the bow tie (I was good up to that point. that one hurt) and finally, 11 exits the same way he entered, crashing.
And, how the heck do you top DT's exit anyway. Not sure that can (or should) be done.
I would have liked that story line to have been a bit longer. Say about three episodes of getting stranded and setting himself up as protector (1), Clara finding her way back to him and gathering a few allies (2) one final big fight where the day is won but the Doctor is lost (3)
The new regeneration cycle was an existing Deus Ex Machina from long, long ago. I'm ok with it because it's a simple solution. The Master has used it (or tried to) at least once so it's only fair the Doctor gets to. I could have lived without it though. I would have been happy with a 12 regenerations being 'more of a guideline' explanation, or a ''well since your the last of the time lords and all that, you get a few extra lives until the rest of us get back on our feet." And that still keeps the Valeyard in play (anyone remember him?)
And while were on the topic of the time lords, aren't they supposed to be frozen in time? OK, true, if anyone can work around that it's the time lords but people who are frozen in time shouldn't be able to do anything. So, how are they asking questions and granting 13 more powerups?
One more thing to explain I suppose.
Still and all, not a bad send off. Thanks Matt, you did the fans proud.