If you go in expecting NWN to be similar to Baldur's Gate, and if you're an RPG purist with a tendency to berate anything different, easier or less complex as "casualized piece of pure garbage", I'm pretty sure you would hate Neverwinter Nights with a passion, as many others with similar attitude and expectation did before you. You control only one player character, you can have companions in your party (although in the official campaign only one at a time), but they will be controlled by the computer, and while you can gve orders to them, their AI is generally quite terrible. And as far as I know, in the official campaigns your companions don't talk to each other, there's no banter, and their backstories and personalities aren't all that great, in my personal opinion. The official campaign has lots of looting, hacking and slashing with trash mobs and not such a great story (again, IMO). Personally, like Ragnarblackmane, I think NWN is a great game regardless, if you ignore the official campaigns and play custom campaigns instead, with better stories, characters and partially improved AI. But I'm not so sure you would like it, as you don't sound very open-minded in this regard ...

NWN 2 is a bit more like Baldur's Gate, with a fully controllable party of characters with personality and banter between them. But it has its share of problems as well, most notably the camera, pathfinding and performance issues.

Planescape Torment looks and works similar to Baldur's Gate, but it's quite a different game, since it's very text-heavy and the combat is not as good. I loved it despite and also because of that, but you need be prepared for it. Like I wrote before in this thread, it's a game where reading, INT, CHA and WIS will get you farther than fighting, STR, CON and DEX. And the setting is very different from the average D&D Forgotten Realms setting of Baldur's Gate.