If someone took their basement, covered the walls with graffiti and stickers, and built a tiny stage...the result would be similar to The Milestone. It's a great music venue, but it's definitely not for everyone. It's small, smoky and in a crappy neighborhood. I saw a women musicians showcase at The Milestone, which included a great show for by The Lights Fluorescent.
Warning: There is a makeshift ATM-like machine at the bar. My friend had trouble with the machine and it's a bit sketchy, so I'd stay away from it.