I've only been out once in Belfast, and that was to the Manhattan or as it's often called, the M Club.
I didn't really think it was that great. There's far better places further North of Ireland where I live, but it was nice to go somewhere different and the music was good. I even got to see Tom from Big Brother who was there that night, although he stayed in the DJ box and VIP area for the whole evening.
Dress Code: I think anything goes really. Perhaps dresses instead of trousers but the shorter the better!