I've packed an Exos 46 around Arizona for the last 3-4 years and it's held up far better than I would've expected. Everything here is sharp, pointy, and abrasive and it's hard to tell the pack has been to so many places. Best damn pack yet, and despite the relatively small size has been able to cram in everything I need for 3-4 days with some bulky addons like an SLR and lenses, ham radio, fishing gear, etc. The stretchy material rocks...
The only snag, for me, is the frame is built for someone with a slimmer build than my fat ass (5'9" (10 if i don't slouch!) and ~205lbs) and can kinda wear on the hips/ass region if I don't cinch it properly for a high ride. Also not the most holster-friendly pack in the world, which got me to go the drop-leg route pretty early on.
The newer models keep getting better too, and I've been seriously considering upgrading (as if I need excuses to boost that REI dividend...)