I use it and it works very well for me as a microblog, plugin for members & blogs, keeping up with other people & news, getting a few good laughs, etc.
I almost feel guilty posting it in these threads, though, since I only follow a very small handful of industry people with Grandma Scrotum, Gonzo and a few others among them. Basically if you are just using it as a marketing tool and/or don't "get" it, it probably won't work well for you.
http://twitter.com/tastytrixie
(yes, I was just bitching about my frustrations with review sites)
and my trans girlfriend:
http://twitter.com/deliacd