SPOILERS
It was all much too fast. It even felt much shorter than it actually was. The whole thing was rushed and it left a hell of a lot to be desired. I'd gladly see a lesser episode cut from the series (the recent "Closing Time" comes to mind) to make this at least a two-parter.
To be more particular, one of the things that jumped out at me most of all was when River was talking about sending a message to everyone he had helped. Definitely could have been very nice and touching, but then it was abandoned right afterwards. The final "question" was clever enough, but it felt too much like an afterthought to have the intended effect. I was also pretty disappointed in seeing that it was just a fake Doctor after all. I don't want to be the jackass who says "I knew it all along it!" in retrospect, but I had a strong suspicion for it being the Tesselecta when they showed up. (Why else bring them up again?) Either that or the flesh doctor. But, besides the obviousness of it, my deeper complaint was that it was a completely underwhelming way to resolve the whole "Doctor dies" thing. After the big deal that was made over it being a "fixed point" and all; sure, it made enough sense, but it also felt like a fairly lazy cop-out for something that an entire season had been building up to.
It was fun, though, I'll give it that. Rushed, fairly messy, underwhelming, but still fun.