I finished it today and was very suprised how well overall the writing and the father-daughter bond was realised.
I agree with RP that they have a bit exaggerated the splicer/alpha/mutant spawn rate. It's also harder now to get some ADAM. First, you have to kill a Big Daddy (Rumbler are particularly mean), then you have to find twice a location for the LS to harvest which in return will be heavily assaulted, and with a big luck you have to deal with a Big Sister (toughest enemy, even on Easy) as well. But the improved shooting mechanics makes that up.
Sound and Art is as always top notch, the level design a bit more confusing and ramified than BS1, but still 1000 times better than most the linear corridor shooters out there.
Overall, I liked BS2 equally as BS1. That means, very much.
BS3 can't come soon enough.