DA2 is worth a playthrough. One playthrough, anyway: I tried to replay it, but just got too bored.
I don't know why, but things that are awesome in
BG2 - exploring, picking up treasure, doing mini-quests - are rather tedious in DA2. I guess half of it is in reused areas, and half in "randomized" treasure in chests and shops(say, you want a ring for 1,33, and you only have 0,66. You need this ring, so you go and do a quest and get some money, you come back, but the equipment in stores is randomized, so the ring is gone). DA2 has some great quests, though, and some very good voicework. But you have companions forced on you for an entire duration of the game, you can't get rid of Varric/Aveline/Merrill/Anders, not ever, so that's a letdown too. Not to mention Hawke's voice(which is fun at first, but if there was an option to go without, I'd take it).
BG1 and
BG2 are definitely The Awesome. Well, like
PS:T, but due to
PS:T nature, you just can't replay it as often.