Of the two, IWD2 is perhaps a bit more polished, has a little more roleplay, but essentially it's still the linear, hack'n'slash type of game the original was. Which means if you liked IWD, you will probably like this one.
You do have to keep in mind the switch to 3rd ed rules, so there will be a learning curve in that respect. But there's plenty of "party building" info on this board if you should need it.
I don't know what potion Pritchke was talking about; usually, for anything important, there are two ways of doing things. But you can get into trouble if you're not careful. Of course, that's true of most games anyway
Nightowl2