I've only heard good things about them, but never used one myself.
I've been using a Berghaus Atlas ever since I began my first trip post-army. It's very tough with thick, heavy duty cordura fabric, and stealthy. I like the LOOK of alice packs, or any old school military pack, but those were all before manufacturers figured out what works best on your back. A few flat pads (if you're lucky) and generic shoulder pads aren't going to be so nice after walking miles and miles. Soldiers used them because they had to. (Though if I was really going to be beating on my pack, such as train hopping, or doing short distance bushcraft adventures, that's a different story)