What kind of evil are we talking about?
Evil people can be quite friendly, helpful, generous, and even trustworthy. It depends on the type of evil, and the type of behavioral traits the players wish to play, and or the DM to accept.
Running such a campaign should be no problem if the players are mature and the DM has a firm grip on the campaign.
An LE for example could be a remarkable force for good. Defending the realm from orcs, giants, whatever. Healing the sick, and protecting the weak...The inner motivations for doing such acts is where we get to the nitty gritty of the alignment. That's what counts.
An NE, deep inside is an uncaring, selfish prick, but if it benefits him, he can do some very heroic and noble deeds. Sure, he'll save the princess, for the right incentive, and if it turns out to be too tough of a job, he's going to choose himself over the princess that's for sure. An NE is most akin to a Han Solo type, that has a little less compassion. With proper guidance he can do some pretty decent things.
CE will be the most difficult. The chaotic nature makes people with this alignment unpredictable. The trick is playing the alignment cool, until there is a moment of stress. The CE can be a mild mannered individual, giving candy to children, and behaving like the all around good citizen...When the plane crashes in the Andes, the CE ( All around nice guy ) will be first in line at the buffet, and first to suggest killing off the dying.
If your players want to run around, steal the king's horse, kill old ladies, and torture children, then you have a disturbing group, and a major problem that goes beyond simple advice from the people of EnWorld. LOL!
GSI