Funny that you mention it, I've been playing NWN2 for the last couple or so days, and I must say it's been my first D&D game so far (what with the crazy dice rolls and stuff) and I'm enjoying it greatly. While it's been really, really, REALLY confusing for me to try and figure out the caps, rolls, skills and whatnot (thankfully I've been able to correct a few things thanks to the character editor), my character is quite quickly getting up to pace. Just arrived on Neverwinter proper, and I think I'm getting the hang of it pretty quickly. My character (a Pureblood ranger) is quite likeable, and so far I haven't seen many bugs. The little of them I've seen are actually quite funny and beneficial (I saved just right during the fight in which the Druid shows herself, and when I loaded the game my party started attacking the enemies while they were talking, so I could practically just sit back and wait them to kill all the grey dwarves).
I'm finding the game quite likeable if a little chaotic being accustomed to Dragon Age's behavioral patterns, and once you get used to the game's pacing I think it's an actually good game. Not the Second Coming, but it's definitely fun and quite gratifying. The party banter has made me chuckle once or twice thus far, and boy did I feel my crotch funny the moment I saw my Druid could summon a dinosaur with twice the health of my tank as a companion (sorry for the mental image).
Once again, I can't understand half of the user reviews in a Bioware / Obsidian / Bioware + Obsidian game in Metacritic, Fallout: NV and Dragon Age II being the other two. Yeah, the game certainly does feel kinda rushed (the fact that you have to set the option to hide or show your helmet with a sepparate editor is an example) but I certainly don't feel it's THAT broken. In my opinion anyway.
Oh, and I've been playing the game + expansions vanilla up until the last session, in which I upgraded to the last patch, so I don't think there's the possibility of me missing a ton of bugs just because I had it up to date.
So OP, to sum up:
1 It works like a charm on Windows 7, haven't had a problem so far.
2 Haven't encountered a "game breaking bug" yet, although I've barely played for 3 or 4 hours.
3 Graphics are not that bad, really. It takes a little to get used to, especially because the character models look like plastic dolls, but trust me, it's not that horrible by a long shot.
4 Maybe you'll do like me and spend some time in the wiki trying to figure things out, but the rules are pretty simple and it's a reward in itself to make sense out of the numbers and dice rolls. I mean, I played a game of Exalted once so I'm not totally new to these things, but I've found the "hardcore RPG" rules on it to be quite enjoyable and intuitive.
Man I need make my posts shorter.