Brand isn't everything. I have a cheap Academy backpack I picked up at a local Sport Chalet (a CA chain store) that is surprisingly well made, but doesn't fit quite right for me. It's okay for day hiking in winter (full of clothes and overnight gear, if needed), but I wouldn't want to wear it for days at a time. It does fit a friend of mine who took it to India for 3 weeks and it came back none the worse for the wear. My regular pack is an old Kelty made from Spectra (not one of the famous white ones, mine is blue) and it is lighter and fits better. Got it second hand right here.

If you know what you want, look for a used one if money is an issue. There are bargains out there if you are patient, do your homework and don't get too excited if you are bidding on eBay. Craigslist may be better since the sellers are usually local.