I don't know that I have yet. I was curious so I set up GPU mining at a small scale with the client and a wallet, but so far bitcoins are not of much value to me.
There weren't any particularly interesting technical challenges making it work, it only took a couple of hours to do and now that it all works it's all kind of boring actually. I don't really care much about all the hyped benefits I see touted on this forum and elsewhere, but for now I'll keep making coins in the hope I can find a reason to continue. I'm glad my additional hardware investment is zero so far because it looks like it will stay that way.