It seems like people are settling on referring to him as the Twelve Doctors and the Other Doctor.
The episode, or the story, feels unfinished to me, so I'm withholding final judgement. Were all the daleks at Trenzelore destroyed, or just the ones right there? Given the events of the episode it seems odd that they'd have only had the one ship there, but I don't know. Did the Time Lords close the crack permanently or not? Did Clara still run up and down the Doctor's timeline or not? Presumably, the first episode of the Twelfth Doctor's era will pick up where this one left off and answer some of those questions.
A new cycle? The Twentyfour Doctors? Good lord.
I knew it wouldn't happen, but honestly, I want the Doctor to die. He's always viewed immortality as a trap. And while the Time Lords have always had the power to dole out additional regeneration cycles, they typically choose not to, preferring to live their lives and pass on. I feel like the Doctor is so old now, and so tired, please just let the poor guy rest. We can keep telling stories about the original Doctors indefinitely; I'm not convinced that we need twelve more.
As for incarnations physically aging, the First Doctor died of it. The Fourth Doctor ages considerably during his period (the actor played the part for seven years) and in The Leisure Hive he's trapped in a thing that ages him 500 years, which leaves him looking really old (they reverse it later). Similarly, the Master force-aged the Tenth Doctor into a CG muppet. The Seventh, Eighth and Other Doctors are all also considerably older looking when they go, and the Other Doctor goes of old age as well, if it wasn't the Sisterhood of the Flame's tinkering with his regenerations wearing off.