I really think the IWD2 website goes into what you can expect from the game far better than I could, at this point. There are several developer's diaries pieces that are especially worth reading. This much I can tell you: the game is structurally like IWD1, but with rather more attempts at diversifying quests within any given area. This doesn't mean it non-linear, but tries to obscure that by putting in several small, local quests among a big one. You're still pretty much limited to proceeding from one area to the next, however.
I'm also not a tester. I'm press.
