Mullens is a pretty average bar. I don't know if average even really cuts it. The liquor selection is pretty "meh". The beer selection is even more "meh", but it is cheap. Like really cheap. Just check out some of their deals:
http://www.mullensonmadison.com/
For example, on Wednesday nights all drinks are $2! There is absolutely nothing to complain about with that.
The atmosphere is pretty okay. It's loud, but pretty open. They also have a pool table and ski ball. SKI BALL! I will be wasting many a dollar here. I figure, if I'm saving money on drinks, you might as well spend that savings on ski ball. Makes sense to me.