I'm in the Cleveland, Ohio area. We have a bunch of GNC's around here. I'm starting to become wary of GNC products. Everytime I go in, it seems the sales people just want me to buy something - anything. They suggest anything and everything. A couple of times, I got things which I later found out had ingredients that didn't mesh with my diet. When I went to take it back, I got a bit of a hassle and (though I can't prove it) am sure I got screwed on the credit I received. I had a $5 gift certificate and they only gave $3-4 back of it and the guy said it equally distributes the discount to all of the products purchased on the receipt, blah blah blah.
So, I'll take a look for it at GNC if I can't find it anywhere else. They also demand your license every time you take something back or say they won't do it. They're more hassle than they're worth, I feel.
I have a lot more success at the health store types of places; especially the supermarkets that specialize in organic foods. The people I've encountered there are helpful and don't care if you buy something from them or not (which is good). I'm sure GNC is commission-driven. Those guys never seem to tell you the whole story behind a product like the organic supermarket people seem to. Again, just my opinion. Your mileage may vary :).