Friday nights are 80s nights, Saturdays are new music, Tuesdays are LGBT night (Tuesgays), etc. Basically, it's a really hip dive bar with a dance floor. Drinks are in plastic cups and the atmosphere is young. It's a great place to finish the night. Ending at Barbs is usually followed with a hangover the next morning, but it's usually worth it.
It's a bit dark, a bit dirty, a bit loud (you can find areas where you can talk though), the crowd is primarily 20-somethings. It's a great time if you know how to meet people or are going with a group of friends.
Get there before midnight to avoid the cover charge. 80s night (Fridays) are the best nights. The first wednesday of the month they do an Emo night.