I enjoyed the episode. Throwing the crack back in as a link between our universe and Gallifrey was brilliant and I get it that even if something that catastrophic heals, there will be scars. Look at our own Chicxulub - a magnetic imprint of the crater still exists today, and that was 65 million years ago. Placing Gallifrey on the other side of the scar just makes an odd kind of sense. And how else was the Doctor going to get a new set of regenerations? The whole "but there were 12 doctors over the planet" argument can be easily explained away because with all of them together, it makes memory of those events very tenuous. Just the events from 3 of them together were mostly forgotten and Hurt's Doctor would go on thinking he blew up his planet, so no paradox. The small bit of irony in this episode is that Matt's Doctor, like Hurt's - the one he tried to forget, also grew old fighting a war, only he was protecting a small town, not one entire planet. My only hope is that the crack won't be snuck into a bunch of episodes again. It was a great plotpoint of Matt's first run but retreading old territory and all that.
In the end, this regeneration sequence was not bad, and it being the start of a new set, it was cool seeing that energy used as a weapon. Now I'm going to invoke the R word, so all disclaimers apply. Anyway, River used her regeneration the same way, albeit on a smaller scale, so why not a full-blooded time lord? The call backs to Matt's first episode were nice, and him removing the bowtie was a nice touch. There was a eulogy, a goodbye, please don't go, then KIDNEYS! Plus the regeneration didn't take 30 minutes! It was long enough to say goodbye without dragging out, and we got to see Amy one last time.
And did anyone else get an odd "Abraham Lincoln Vampire Hunter" vibe off the Doctor at about the middle? I half-expected him to grab an axe!