I'm mining second week now. Didin't go crazy and buy highend mining rig for this, just using the spare clock cycles of my gaming pc. It gets ~400 Mhash/s with oc'd 6950@6970 radeon. The market is too risky for me to invest a dime for except electricity, but I made about 100 usd at first week while mining BTC. Now the system is pointed towards namecoins, those seems to give better returns with current trading rates.