The mid-season finale was slightly disappointing in that the rather lovely Lorna and the amusing Strax ended up mortally wounded. In a not-very-surprising twist River Song was revealed to be the offspring of Amy and Rory, and was probably the kiddiwink seen in the first two episodes of the season. She also has some Time Lord DNA and is able to, at least partially, regenerate.
The actual ending was slightly strange. The Doctor ran off in the TARDIS, leaving his companions and River behind, searching for young River. At the end of the episode it showed a skeleton at the bottom of a body of water, clutching a sonic screwdriver.
The Doctor’s ‘death’ in episode 1 also needs to be explained. The most obvious solution is that the ganger Doctor gets reconstituted and allows himself to be killed. That said, the real Doctor could do that, and fake Doctor could be made permanent (this could provide a handy get-out clause for the 13 incarnations limit Time Lords have, although this is more of a law of man than nature [see: The Deadly Assassin]).
The first half of the season was generally good, especially the excellent first two episodes, though the finale was a little lacking in tension. There are rumours that Rory and Amy will leave the Doctor at the end of the season, presumably to look after the young version of River.
Matt Smith should be around for another few seasons at least, (I think he’s guaranteed to be there in 2012, and maybe 2013). It’d be good if they got him a companion (or two) from the past instead of a modern day girl. Well. That, or Sally Sparrow, obviously.
It also appears that Moffat’s taking a different line to RTD regarding the daleks. Specifically, they’re going to be used less often, which I think is a damned good thing. They’re great villains, but were being over-used. I hope that the increasingly overblown season finales get binned too. Dobby the House Doctor was not a good look.
Lastly, 2012 is going to see fewer episodes. The BBC first claimed this was because Moffat, who also writes Sherlock, was too busy, a claim the man himself refuted in plain terms quite quickly : http://www.bbc.co.uk/news/entertainment-arts-13784334