There's some nice stuff up on the third floor, but most of it is horribly overpriced. I'm sorry to say it, but most stuff at Mike's is pretty much junk. I tried out a bunch of their vintage stompboxes, and every single one of them had something wrong with it. One had a broken control, one sounded weak, another hummed so loud I thought it was going to destroy the amp's speaker.
Pros: a lot of rare stuff
Cons: most of it is poor quality and/or overpriced