Don't listen to the haters. DA2 has some bugs (a few that are REALLY annoying, that I'm confident will get patched out).
But story and character-wise, it's possibly the best game Bioware has made. Seriously. Nothing else comes close to actually making your choices feel like they matter. I connected with the characters even more than those in Mass Effect, which is pretty impressive. It's absolutely worth $40, and it's worth full-price, in my opinion.
I think most of the ire is because it's not a typical "save the entire world from evil" type of story. Some people have said it doesn't feel "epic" enough, which is BS. It's character focused, and it's great BECAUSE of that, not in spite of it.