The Macpac Cascade 75 (Size 3) has served me brilliantly over the years.
It's still in good condition as it's been used for international backpacking rather than bushwalking. You can't get much better than this when it comes to backpacks, particularly if you're wanting to do multi-day hikes, and it's priced very reasonably at only $175. (+p&h outside Hobart)