The advantage to milsurp like ALICE is that it's very inexpensive and rugged, but there are certainly more comfortable civilian packs out there. Military surplus is still the best bang for your buck in my opinion though.

I use the "Hellcat" modification for the ALICE pack, which basically replaces the stock shoulder straps and kidney pad with the MOLLE straps and kidney pad, and it makes a world of difference in comfort IMO.

It also involves strapping the Molle MSS carrier to the bottom of the pack and frame, which can be used for your sleeping bag (when loaded it doesn't flop around or bounce off your butt).

Weight does add up fast though!