I think that the description of the facilities are fairly well captured in other reviews, in particular Kat F.'s review. One thing I would add is that the sight lines are pretty good from almost everywhere because the stage is really high. This is really useful if you are, or will be attending a concert with, a shorter person. You lose all of the benefit of the tall stage if you stay on the top or second level though, so if you're short try to get down to the pit.
Lee's is not trying to be something it's not nor not as cool as it thinks it is (to the extent a building has an ego). I know others have eluded to it, but Nirvana, Oasis, the Smashing Pumpkins and others all played here before they were big, so give it some respect as the musical icon it is.
The Dance Cave (upstairs) can be a fun and easy thing to do after a a couple of hours of live music. But know that the average age of a Dance Cave enthusiast is about 20.5 so you'll likely feel like you are back at a campus nightclub, which can be fun if you're in the right mood.