I read up about it once and considered using the spare time on my PC to run the mining client. Then I read that at this point the chances of actually "finding" any coins through mining were miniscule unless you are part of a pretty big team and the payout didn't seem worth it considering you would have to split the take with so many people. At this point I don't think you would make back in mining for coins what you'd use in electricity from running your PC.
From what I understand though, like the money in Second Life
, you can trade Bitcoins in for cash along with being able to make online purchases from sites that accept them.