Have DMed an all evil Lankhmar campaign. Worked well enough but the PCs never really acted all that evil IMO. It just became another 'heroic' campaign (guess that was mostly my fault).
I have played in an all-evil campaign - it sucked. First session we start out in prison, in chains. The PC thief (this was 2nd ed)
without any lockpicks or tools of any kind picks the locks of his chains with his
fingers. He then proceeds to ask each of us what we will give him if he frees us. We, of course, promise the world.
We get free and in the running fight out of the prison (which employed Ogre Magi as guards - yes we were all first level) we come across a few items of magic and money. We agreed to split the stuff up once we were out of the city.
We get to a neighbouring town and identify and divide up the stuff. The thief gets a pretty big chunk and I end up with a +1 Glaive. As a Monk that wasn't bad but I'd have to wait several levels to gain the proficeny. Oh well I thought - at least I could sell it.
We go to sleep in the inn.
The DM asks me to bring him my character sheet. He looks at a minute then rips in half and says - "You're dead. The thief killed you."
I was a little stunned as I had locked and barred my door and had no window in the room but I wasn't mad. The tohief player then turns to me and says "You just don't know how to play very well do you? That was pathetic locking your door, my thief can open anything. Since you locked you door you directly challenged me to open it - I was just following my alignment when i killed you."
I looked at him trying to figure out if he was serious or not.
I got the feeling he was and the other players and the DM were
nodding in agreement with him!
I left that group never to return.
Another mixed alignment campaign I was in the DM vetoed the Paladin I wanted to play because there were evil memebers of the group that the paladin wouldn't associtate with. I said fine and made up a CG thief (there was a CG Cleric and a N Fighter as well). The evil PC showed up once and got himself killed by a rival evil cult when he tried to bust in on one of their rituals. He was a CE follower of Cyric. The player never came back (but I could have played my paladin if he had never shown up in the first place

)
So all in all I don't really like evil PCs and have never really understood the appeal. If thats what your group likes then I have no say in it - just don't try and bring an evil PC to MY table.