I've used many different brands and styles of hiking packs, from high tech ultralight to military "unbreakables", and I always come back to Osprey as a nice middle ground.
They're the most comfortable packs I've found, and for the most part they're extremely well designed. People who say they aren't durable enough are nuts. I've carried mine through sharp talus fields, clearings filled with brambles and thorns, tossed them down snowy slopes, you name it. Not a single rip or tear on any of my Ospreys, just a few scuff marks.
Right now I'm running an Osprey Kestrel 48 litre as my extended stay camping bag. It's great.
If you're going to put any serious mileage on your pack, get a civilian styled hiking bag. Forget the pretty military styled packs we all tend to love here, and get something that WONT kill your back. You aren't getting shot at in Afghanistan. You don't need a milspec pack. I carry a hardcore molle bombproof pack as my day bag / bushcrafting bag (since it looks cooler and I'm basically still a kid playing with his green plastic army men) but honestly they're no good for real hiking and mountaineering.
But whatever you get, just make sure to try the bag on before you buy it!! The most important thing is that the hip belt actually rides on your hip, and thats where the majority of the weight of the pack will be located. The shoulder straps shouldn't be carrying much weight at all -- just stabilizing it. If the belt rides up on your belly even an inch (like a lot of military packs!) DON'T BUY IT! Get one that fits your torso properly.