Fit is really everything. One thing I really liked about my Lowe Alpine Contour IV pack is that I was able to remove the aluminum staves and recurve them to fit my back. Everybody's different -- it's like buying a handgun, no one can really recommend Model X as a 100% sure-fire winner.
Once you find a pack that fits you, you should get the pack that has the capacity that you need. Are you going on week-long trips into the backcountry? Then you'll need something with at least 5,000 cubic inches in capacity. Or are you going on long weekend type trips? Then something around 3,000 cubes will do fine.
I have the aforementioned Lowe Alpine pack for week-long trips and a Blackhawk Phoenix pack for long weekends. I am in the process of ordering two BH accessory pouches for the Phoenix pack so I can stow my tent outside the pack.
I am very happy with my Phoenix pack but in hindsight I probably would have gone with Eagle's Becker pack. It has more capacity and is made in the USA.
Hydration system compatibility is nice, but not essential. I use a Camelbak Maximum Gear HAWG as the hydration system for both packs. The Camelbak MULE and HAWG are nice for day trips from your base camp.
I second the recommendation to look at the commercial manufacturers as well as Blackhawk and Eagle. They might not have everything in kewl tactical black, olive drab or woodland camo but their stuff works very well.
A good place to buy commercial stuff off the net is Campmor, located in Paramus, NJ (http://www.campmor.com). For the tactical stuff, I would also recommend Geri Weaver at Geared Up.
HTH,
Justin
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Justin T. Huang, Esq.
late of Kennett Square, Pennsylvania