I used a Berghaus. Well designed & very durable. Mine lasted for 10 years & only got thrown after a family of mice ate most of it when I foolishly left it in the garage.
My tip would be to take the smallest rucksac you can get away with, because whatever size you take, you will always fill it. I managed with a 40 litre pack but my friends who take 55 & 60 litres moaned for the entire year!
<PRE>Size is important ;-) Not too big or you will fill it with stuff you don't need and then wont be able to carry it. Make sure its waterproof or that you buy a cover for it. When I was in Asia quite a few times my bag was chucked on the back of a truck or the roof of a minibus and then the heavens opened and jesus can it rain out there!! Make sure it can be locked up securely too, just in case. One more thing, clothes and footwear are dirt cheap out there so you may want to get t-shirts and stuff as you go along. Don't take really posh stuff with you as it will just get battered.... Have fun!!</PRE>
I found the specialist suppliers the best. In OZ we have Paddy Pallin, Kathmandu and Mountain Design, all of whom have a range of packs. Take your time, ask heaps of questions, have them fit you and adjust the pack. They will put stuff in it to give you a feel for what it sits like. I found top loading packs annoying and ended up with a Mountain Design model, made in OZ and very happy with it. It also came with a day pack, ggod for taking on the plane. Good luck.