I am surprised that people would actually out rightly ban evil characters. It is in my opinion that a good DM should cater for all the tastes. Although there should be a screening process to eliminate those who simply want to abuse there alignment.
It is probably one of the greatest role playing experiences if you carry out the alignment correctly. Far too many do not see beyond the classic stereotype of evil characters.
Currently I am a lawful evil character in a group where chaotic good dominates. A problem some may think, but I have concealed my alignment with the excuse that it is to prevent others from scrying on me.
Downtime is really where and when the true character shines. However I need to pull aside the DM for a session. Whilst the rest of the group upgrades their equipment, I am off role playing the underlying motives for my character. This means that the group has no idea that my character is evil.
Since I am more of role player the rest of the group believe it’s a time when I can generally acquire more exp. so no suspicion is aroused.
However for this to work you need to have a very flexible DM and a group who don’t role play during down time.
There is always the underlying fact that eventually there will be a clash of interest... But that is when things get interesting...
Remember: Evil is just like cola... there are five different flavours ^-^