Hey guess what, my friend did an article on
bitcoin mining, comparing many different video cards on how they perform. He even put together a 1000W+ monster rig that generates $3600 per year!
Here's the chart that shows the total net profit over a year (so the cost of the video card itself is subtracted, but not the cost of power consumption)
As you can see, it's not worth using an Nvidia card...
And here's the power cost per year (BC would be in group D)
So for Ulic who is running two GTX 260's, he is probably spending about $400 a year to make his $360 worth of bitcoins.
Handy chart!
Here's the chart of dollars per day, followed by power cost per day, so you can do a direct comparison on your card: