I have a Hammerhead too, bought it from REI for MSRP of $85, but I went back in and got $20 off when they went on sale for $65 over last weekend (don't think they are still on sale, I was just there today and it looks like the REI brand hydration packs are on sale at the moment).

I love the size, and how it fits, but the strap ends tend to flop around, and I wish the mesh side pockets were a bit taller so they could hold a Gatorade bottle securely. I use a bunch of rubber bands on the straps for now, but I might modify the pack a bit with Triglides. That would involve cutting the sewn stops off the ends though. The outside mesh pocket and the X-bungee are awesome. The reservoir is a pain to dry, although I'm sure that most reservoirs are. I bought a Camelbak Cleaning Kit for the hanger, you have to cut the hanger to fit the somewhat shorter 100 oz. Nalgene reservoir. The swiveling magnetic bite valve is awesome.