I'm quite happy with my ARC'TERYX bag. It gets used 6 days per week (4 bike commuting and two 3hr train rides per week). Also, only flights are such with no discernible wear after 4 years of heavy use.

Never tried it myself (mine is 20L):

Chilcotin 8 Backpack / Packs / Daypacks / Arc'teryx / Arc'teryx

Haglöfs makes some good stuff as well (Gram 3 may be what you want):

Intense Unisex | Haglöfs