I'm getting 140MH/s on my 2011 iMac's AMD Radeon HD 6970M using DiabloMiner.  I only run it at night (off peak electricity) during winter (instead of running a heater) but it's been quietly mining away.  I'm using deepbit.net as a pool and find I mine about 0.01 BTC per day.  I started doing this just out of curiosity, and spent my first BTC last week when they were around AU$170 per BTC. I am optimistic about the future of bitcoins and would love to set up a much bigger mining rig running off solar power. Waiting on delivery of a Butterfly Labs ASIC miner now (bought with BTC I mined myself) and, from some of the posts I read here, I suspect I might be waiting a while. Lol.