It runs pretty smooth for me and I don't have a high end system at all really.
What does bother me is that it just feels like another standard iteration of CRPG-ness. It doesn't innovate anything really, and I'm so tired of the boring old fetch and investigate quests.
The controls feel kind of sluggish, and not in a video lag kind of way. For example something I would do in Baulders Gate 2 was use my rogue to check for traps, scout ahead, and then open a door to a room I knew was full of bad guys. At the same time my two spell casters would hurl fireballs, or some other area effect, and clear the room out. I did that all at the same time too. It doesn't feel like you could pull that off with the same precision in NWN2. You also had to be careful with your area spells because they could hurt you too. I blew up my rogue a time or ten. No longer. You can unload your worst area spells right on top of you and nothing will happen.
It also shows how bad the AI is. In my last play session my wizard got some Gas spell that causes death in weaker opponents. Do the bad guys avoid my gaseous cloud of instant death? No they march into it one by one until there is a pile of corpses laying at my feet.
Party AI is a little better though, or maybe battles just don't require the teamwork. I remember in Baulders Gate 2 needing to pause the game and ordering each of my six party member to do their attacks on their own and who they should be attacking. In NWN2 I can let the AI do its own thing and for the most part don't regret it. Except for the druid. She has the habit of turning herself into some stupid little forest creature instead of smiting our foes with her magical prowess. It wouldn't be so bad if she turned into something awesome that could fight, but she turns into something like a badger that misses most attacks and when she does hit it's for a paltry amount.