Tuthrick: Playing as evil in Baldur's Gate can be a bit problematic in my opinion, especially if you want to role-play based on your alignment. The reason is, well, many dialogue options that are evil, are actually more "asshole-like" than "evil". It can be fun, but if you're trying to be "smart evil" that can be quite tough, though. Plus, the evil options have lower rewards, so the game might be a bit more difficult.
CFM: All good points, especially about "asshole-like" dialogue options. You got me thinking: Neutral Evil certainly doesn't mean being a rude dick with every last person you come across. The scariest villains hide in plain site with the most pleasant of smiles, and bring out the ruthlessness when it is most needed or beneficial. Maybe I can take that angle: heroic quest do-er, but will kill for my reward!
Tuthrick: Other than that, it's really nice to approach the game from a different angle, especially in terms of joinable NPCs. The ones with evil alignment tend to be quite amusing and some like to argue with others (mixing all types of alignments in your party is even more fun).
Sticking to one party composition is way stronger, but changing things as you travel will let you have a lot of possibilities. Some of my most memorable playthroughs were, when I only reloaded because my PC died. I got to the point where I had almost every available NPC in my party during the course of the game.
CFM: It sounds like if you can keep your Reputation score somewhere in the middle range (like say between 9 and 12), then any combo of NPCs will stay together, without turning hostile or otherwise leaving on their own. Would you all agree with that?
Yes, if you keep your reputation around middle, you can have NPCs with all kind of alignments in your party. You can have your rep even at 3-18 range, some NPCs will complain, but they won't leave (rep 2 is when good and some neutral NPCs will leave or fight you and 19 for evil ones).
As TrollumThinks mentioned some will argue a lot and can even fight eachother, where you can't control them until the fight is over (they'll have purple circles, like in a multiplayer game). Some characters have unique insults for someone they escpecially dislike, like Kagain for Yeslick. Those quarrels can be quite amusing and addresses one of the complains that the NPCs in BG1 are almost silent.
