This thing is awesome. It has enough space to hold my lunch, which is usually huge and my work clothes. It has enough room left over for a sweater and there's an expandable outer panel to hold a pair of sneakers or a 7 liter pot.
Best part is, the suspension. It has these aluminium stays in a "X" configuration that keeps almost the entire pack off my back. The only thing that touches is this really open foam pad at the bottom of the pack and my shoulder straps. Everything else is open mesh and the wind really wraps around and into that area on my back to keep everything cool.