Derek P.wrote a review of Osprey Packs Momentum 34 Backpack - 1920-2040cu in on June 14, 2011
Just got mine today and I am floored by how much space it has for how small it looks. I even loaded it up with everything I would ride to work in (about half full with tool kit and clothes) and did a a quick 10k ride to see how it felt. I am very pleased. I use only one pack for everything and I can tell this one will do it all.
I returned a Metron 35 to get this instead and for me it was the best choice I've made yet. Although only one liter larger in capacity, the Metron is bulkier and heavier... and the top of it sticks up so I can't bend my neck up to look forward on my road bike. It would be okay for a more upright riding position.
Either way, the Momentum is better than the Metron for commuting and as a day pack. Buy it.