Minnepolis put in a system last summer that was apparently pretty successful. Even though I have my own bike I became a member (for a reduced rate of $45 a year). I figured there are times when I'm downtown and don't have a bike that it may come in handy. Mostly I just wanted to support the system.
I was worried that vandalism and theft would be a major problem but not so far. They're not that easy to steel and if you did there's not much you could do with one. They're unique enough looking that you wouldn't be able to sell it to somebody else.