Could Protoshares be the beginning of Nvidia mining?

I'm currently mining protoshares, making about $15 a day compared to doges $6-7.

This is quite interesting. Still is this the most profitable method for nVidia, Supa?  😉 Just asking, because I did not have ATI card capable of mining, so maybe I could give the GTX 660 a try there 🙂

What do you made the about $15 per day on what GPU?