Don't waster your money at GNC!!! And don't waster your time asking for advice from the dipshits that work there!!!
I've been using Instone's Performance Intake lately and find it quite good. It's got only got 14 carbs, 7 of which of fiber, as well as some healthy fats & CLA. I limit my carb intake during the week, so this is a perfect choice for me. It also blends up nice and thick, kind of like Myoplex, so it actually fills you up a bit.
My favorite MRP of all time though, was Sportpharma's Nutriforce!!! Mix that baby with 15 oz. of skim milk and it tasted like a milkshake and it already had 5 grams of creatine in it! That was years ago, but I'm still bitter that they stopped making it!