A couple of days ago, I finally used it "for real".
A client of MySQL's uses a system called projectpath.com. And when I first went to it, I saw that it is OpenID enabled!
It's kind of a pity that MySQL.com isn't an OpenID provider for it's staff, like Sun.com does, so that I could have used something like "http://openid.mysql.com/mark.atwood" for it. Instead I just used my personal OpenID of "http://mark.atwood.name/".