Delixe: Neverwinter Nights 2 Platinum just went up on Steam €9.99. If you haven't bought it yet, now is the time.
Foxhack: What's the deal with this game, anyway?
It doesn't seem to include Mysteries of Westgate, at least not based on the store page.
Vanilla NWN2 is flawed. Fun characters, but FAR TOO MUCH content, and badly paced. It doesn't introduce the most unique/fun parts of the game until halfway through, and by then you are almost certain to be burned out of it. It is kind of like Baldur's Gate, only slightly worse, and a system resources hog.
The first expansion is at the same time an independent campaign, and what may be the best CRPG experience since Planescape: Torment. Extremely worth it for that price just for the first expansion. Much better paced, writing is considerably more solid than the base game's was, all in all an excellent experience.
Dunno about the other two expansions, never got them, base game plus first expansion were once like 15 bucks on Gamersgate and there's where I got them.