Interesting episode. Not the most fun episode, but very very good. Donna is quickly becoming my favorite companion (which I would have never guessed). I love the buddy relationship; she challenges the Doctor and fills the gaps in his personality better that Rose did (in my opinion).
I feel this episode pretty much confirms that the Doctor IS NOT
regenerating this season. They're just laying it on too thick. They want us to be on the edge of our seats, expecting a regeneration, then whatever really happens catches us off guard and blows our mind.