I'm usually pretty good with NPCs. I'm never an evil character, and even when I am, I'm LE and just stare them down if they're getting annoying. I've never actually killed any NPCs, but in the current campaign I'm in, we've come pretty close.
The other players, well, hmm. How do I talk about them? One's CE, and the other is CN. They have a tendency to make the NPCs fear us, and run. If Reputation was part of our game, I'd be the only one with a large positive number. Granted, the warblade and sorcerer would have a positive number as well, but not high. The other two would be in the low negatives (especially the dragon). Heck, in a previous campaign, one village apparently found out something they shouldn't have (or rather saw something they shouldn't have) so despite being of a good alignment, they had to eradicate the entire populas so no one could say anything. Needless to say their alignment's changed (even the half-celestial).
I've been a part of a one-shot group who, despite being N or CG characters, would randomly all become CE characters, sell all their loot to the townsfolk, then steal it all back, and do it all over again in another town. When they got to a town that already knew about what they were doing, they massacred the entire town. Then they got upset because the DM wouldn't give them any XP for what they'd done in a ONE-SHOT.
I remember one friend being a LN fighter, questioning people and failing his diplomacy check horribly, not getting the answer he wanted, and then killing the NPC for giving him that kind of answer.
You find all kinds.
I'm good with NPCs, and I get rewarded for that. Everyone else beats, kills, maims, badgers, and scares the NPCs and get what they deserve for it (ie no magic box that allows you to summon a mercane who'll sell you any kind of magic item you want for the right price). Not the that others don't take it out on everyone else later.