If you take in more calories than you need, you will gain weight. There's a good chance it will make you fat if you're taking in more than you need to gain lean muscle. That's why I suggested using it at 1/4 strength: easier on the stomach and less likely to make you fat.
I'm currently negotiating for either 10/20 lbs of Optimum Nutrition Whey or 20 lbs of Nature's Best Perfect Rx. I'm leaning towards the Perfect Rx, but I'll have to wait on the surface shipping quote before I make my decision.