Coelocanth: I'm not clear from your post if you've played the expansions for NWN2. If not, I'd highly recommend both of those. Mask of the Betrayer takes you into epic levels and has a pretty good story to it. Storm of Zehir is a lower level campaign and is light on the story side, but some of the new game mechanics are awesome and overall it's a really fun expansion.
Finally, not an RPG, but well worth the 20 bucks, as it's an awesome puzzle/engineering game (if you like that type): World of Goo.
I'm playing through Mask of the Betrayer myself for the first time right now. I'm finding its story is more engrossing than the original campaign, nor do I mind the "curse" so far. Some of the new classes are also a lot of fun.
Coelocanth--- how much RAM's on your machine? I'm running XP but currently only have 1 GB. My computer had no trouble with NWN2 original, but has bogged a bit in places with the Mask expansion. I want to get Storm of Zehir, but the recommended specs for it have been raised to 2 GB, so I'm wondering if it's time to bite the bullet and add more RAM before installing Storm of Zehir. Have you noticed much lag increase?
And back to Almak's original post... PuzzleQuest may be worth a look. If you've not heard of it, the best description is probably "a mutant meld of Bejeweled and Magic: The Gathering, only it's -good-!" There are RPG elements, the story's not earthshaking but adequate, and you can walk away from it for weeks at a time and not have any trouble picking up right where you left off. It also lends itself to being played for small blocks of time (10-15 minutes), when you don't have time or don't feel like loading up your Big Monster Game of the Moment. Replayability is also high.