I travel carryon only and this bag is just about the right size but I find it incredibly uncomfortable. It's way heavier than it needs to be and the straps are so uncomfortable. I know the materials are durable and can take the abuse but I'd easily trade for something different to shave off unneeded weight. Maybe less padding on the back/laptop pouch? But my biggest grip is the mesh panel on the main compartment has too much stretch. Even though I pack with packing cubes, the mesh doesn't effectively hold in the items so everything falls outwards, which I think is worsening the weight distribution.
Here's a secret. The Hynes Eagle 28L Aurora Convertible Flight Approved Carry On Travel Backpack is the identical bag, about 1/2 the price, and a little lighter in weight. Sure, it's not as bulletproof, stylish and long-wearing as the Jet Pack but it is in all other respects, the same bag. I don't know which came first.