I just played a 16th level Githyanki Psion in a one-shot evil game this past weekend. It was really fun, although I didn't get to "build" the character (all the characters were pre-generated by the DM so I didn't know what I was getting until the day before).
As someone said, there are lots of fun roleplaying opportunities. The party consisted of a tiefling, a fallen aasimar vampire, and a half-fiend something-or-other, and then a human and a sun elf were-leopard assassin. I kept referring to the human and the elf as "primes" and ignoring anything they said and basically acting like I should have been leading the party (based on my superior intelligence) even though the half-fiend was really the leader.
Fun stuff.
As someone said, there are lots of fun roleplaying opportunities. The party consisted of a tiefling, a fallen aasimar vampire, and a half-fiend something-or-other, and then a human and a sun elf were-leopard assassin. I kept referring to the human and the elf as "primes" and ignoring anything they said and basically acting like I should have been leading the party (based on my superior intelligence) even though the half-fiend was really the leader.
Fun stuff.