Cosmos Cafe is yet another venue that is really a restaurant, but doubles as a nightlife hot spot on the weekends. North Carolina's laws on serving alcohol make it nearly impossible to just open a "club", so you see a lot of these in Charlotte, especially downtown.
The staff is super friendly and doesn't hassle you for walking in and realizing "Saturday night" hasn't started yet because the dining patrons still haven't cleared out. So don't be afraid to check it at 11pm and then come back again at midnight or 1 if it's still slow. I've never been here to eat but it's a great place to stop in for a late night weekend drink to see what's going on. People dress nice and behave well. So you can actually get an expensive drink and not worry about someone elbowing it across the room.
There's plenty of seating on both the first and second floors and they have a respectable, if predictable, Scotch selection that helps me keep them in mind when I'm downtown, so I'm sure the rest of the liquor options are pretty good. Coming from Illinois where you can buy booze at grocery stores, it's depressing to walk into a bar in Charlotte and only have one or two choices. Cosmos expands the horizons and I appreciate that.