NWN2: My take:
Much like the original campaign in NWN, (or at least as far as I've personally gotten in both, and have heard from many others) is pretty boring and poorly paced. Some people had suggested to me that in NWN2 the pace and quality of the OC picks up after Ch. 1, but I have failed to observe that so far in playing NWN2 OC Ch. 2 up to right before setting off to clear out a keep. I quit playing again at this point, and even the latest 1.0.6.973 patch hasn't gotten me to do anything other than patch the game, and make sure that it was still functional. I'd still rate either game in the 7-8 range if I were do so numerically, they're OK, but really no better than many other RPGs, and worse than many others as in I've enjoyed Disciples II, G3, and Divine Divinity more of recently played games. Worse recently played games would be the likes of Titan Quest, Dungeon Siege II, Oblivious, Spiderweb games(any, they never impressed me, overly amateurish relying primarily on the captive mac market and community goodwill), Dark Messiah of Might & Magic(not an RPG, but still...), etc. As to games that I've probably liked about the same, I'd probably dump in the likes of Fate and Dungeon Lords(I got the CE for $5, and have actually been seriously playing it recently. It certainly had much more potential than many other ARPGs, although it is unfortunate that it was never really finished and that they fucked over most of their customers... The combat and dungeons in it are enough to keep my attention for the moment, and actually the combat seems to be much better than the usual mobbing tactic of all other ARPGs).
NWN1, I have relegated to playing only under linux, and while in linux with spare time now, I'm more interested in seeing what I can get up and running under the latest wine release or Cedega 6(see thread in general forum).
As to buying NWN2, well I bought my copy as I got it for $25 last November, but unless you can get it for that price or less, I'd wait and see how any third party mods turn out, what Obsidian/Atari release in the way of new official material, and persistent world development if that interests you, otherwise, if you don't have it, NWN1 Diamond package may suit you better.
Both games look fairly similar, especially when you play with the camera zoomed out to max, like I usually do, but zoomed in max or close NWN2 does look better but I find that to be unplayable. Camera control is awful in NWN2 and non-existent(panning/angle) in NWN1. Gameplaywise, they feel and play much more like an action RPG, although the l007 tends to not be as ph4t. The best thing going for both games are the toolsets and what might possibly be made with the engine.