I have the one from Cabelas( bow/rifle pack) it work really great for Bow or gun, very tight fitting has H2o holder for easy use, very good pack for packing back in.
I'd definetely have to second the Badlands 2200 pack. Great internal frame pack, expensive, but rugged and has an unconditional lifetime guarantee! rip it, break it, tear it.....no problems. Send it back for a full replacement/fix. Ihave the 1999 version of the 2200....Guess where it was on the opener this year? Right on my back with my bow on it!! Buy it! I think you'll be happy.
It all depends on your budget.... I personally bought a Camel Back and I love it. I had to do some minor modifications on it to be able to strap my bow to it. If my budget would've allowed me to I would have gone with a Badlands pack they are awesome. The Camel Back I have holds 100 oz. of liquid and it also has enough room for me to throw in a jacket, food, flashlight all of the works. The only downfall to having a hydration system is the weight. Well I hope you find a good one.