Man, is hard to make a Berserker playthrough, most of the good XP quests gives you A LOT of good karma, so you can't do them and this makes level up a lot harder too.
I'm not talking about slaughtering everyone in a town - this is dumb, not evil - but most quests don't have a "pure evil end", is more like being a jerk all around or causing some damage to a comunity or particular group than the black & white definition of evil.
It's interesting that I'm a slaver but didn't had any problem in the NCR, Tandi and Westin talked to me like nothing happend.
I had 56 good karma though (Wanderer), maybe this explain things.