I've been playing Neverwinter Nights 2 and its two expansions, Mask of the Betrayer and Storm of Zehir (just started) for the past couple of weeks since I've been stuck without internet at home. I just had to say how pleasantly surprised I am by the games. The original NWN annoyed me so much that I never really gave it's sequel a chance but I'm so glad I did now. Each game has been entertaining in unique ways, so even halfway through Betrayer and just starting on Zehir, things still feel new and different to keep me playing.
The main game has a good sense of power progression and takes your character on a very interesting arc. This one is less about character and moral choice than it is about an epic fantasy war. You can even slay a dragon if you get good enough. That's supposed to be cliche, but how many games do you ACTUALLY do that? You just get 1 main character in this one, plus set companions and they go from level 1 to about 20.
Mask of the Betrayer continues the main character's story from NWN2 so you go from about level 20 to 30. Starting out at such a high level and getting high level companions is a pretty unique situation. Instead of a high fantasy epic tale in this one, you get more of a character driven story with some very interesting twists that keep this from being too 'standard' as far as D&D games are considered. The main character has an interesting attribute that would be too much of a spoiler to mention, but does provide some cool moments and interesting things to think about. Moral choices in this game are much harder to make in this one. I'm less than halfway through but I can see how people compare it favorably with Planescape: Torment.
Storm of Zehir is one I'm just getting started in, but it's the one I'm most excited about. This one makes a lot of improvements on conversation UI and party interaction over the last two games. This one starts with all new characters at level 4 (though you can import your characters from the other campaigns at their super-high levels. No idea if the game scales for you or if its just a breeze) and this is the first game that allows you to create your own party of 1 to 6 players. It can be played cooperatively online, and it adds to the standard D&D fare by replacing the standard overland map system (pick a location, loading screen, arrive at location) with a sort of Final Fantasy 7/8/9 map you can physically move around on with wandering monsters, random and special encounters, and checks against your character's many attributes and skills to add a big exploration aspect to the whole thing. The only drawback of this one that I see is that there's some definite MMO bleedover into this one, in that I've already done a 'click on 10 boxes' quest. Since I was doing a more intellectually challenging investigation at the same time, I'm willing to overlook that little tidbit.
There have been a few annoyances in the series. The first game has had a number of potentially game-stopping bugs. One involved a boss encounter where the boss didn't spawn, resulting in a neverending encounter. I had to access the console and input a code to bypass it. Apparently the bug has been in since launch and still never fixed. A bug with the installation of Zehir causes all dialog in Betrayer to go away. It's fixed in a patch but in my no internet house, patching has been quite a chore. Many of my personal complaints about NWN2 are addressed in its expansions. Conversation design in it never let anyone's stats but your main character's matter, but in Zehir they've fixed it so that all characters in the party can contribute to a conversation, often with unique options for each one. Betrayer and Zehir both auto-save more frequently to try to match current trends in game save design. NWN2 basic forces you to retrain your brain to save manually (quicksave is fortunately an option in all 3) as often as possible, but you'll lose progress until you re-learn how games used to be played.
So yeah, try these out if you need a winter fix like I did. You should be able to get NWN2 and Betrayer in the Gold edition for under $30 and Zehir for about 30 too. You'll be getting lots of bang for the buck there.