Cell Block has a great bartender in the back on weekends--always ready to give a great suggestion as to what to drink. I've never had a drink (even mixed) cost me over $5 at this place on weekends, so it's not overpriced like most of the Boystown bars are.
As to the decor, yes, it's a little seedy looking, but looks can be deceiving. Yes, there can be some guys walking around in leather chaps, or underwear and chains, but c'mon...it's a leather bar. So it's not as fashion-forward as Sidetrack--there's no problem with that.
It's also nice to find a bar that's not too overcrowded, that doesn't play the music too dang loud, and that you can hold a conversation in. It definitely won't be for everyone's taste, but at least everyone is welcomed when they enter. It's definitely not as exclusionist as some of the other places on Halsted.