After a few rides, I really like the Blowfish. It's so named because you can expand it if necessary by unzipping a section (like some luggage does). Closed, I can carry snacks, my radio and a camera and if I want to add more I can expand it. I looked at the M.U.L.E but felt it was a bit big.
The Blowfish is perfect with a big reservoir, an outer pocket and several inner pockets to organize the small stuff. I fill it about 2/3 ice and the rest water and it pretty much stays cool all day. Another nice feature is a sliding sternum strap (the front chest strap) which allows me to slide it down to a reasonable level (this is a necessity for us taller folks).
It has a small zippered pocket at the top for an MP3 player - another cool feature.
I'm now a Camelbak convert - it's well engineered and the reservoir has a lifetime warranty.
More details here.
