I bought the Stratos 40 because of my experience with my Stratos 24. These are cunningly designed packs, feature exceptional breathability, and are so comfortable that you may not take off the pack when you stop for a breather. I think that this pack is best understood as an assault pack. Both the 24 and 40 liter models are exceptional tools for the summit assault, and the 40 will carry enough to get you into the backcountry for a couple days. They are purpose designed trail and mountaineering packs. They're not designed to be heavy load haulers, and neither are they book bags.
Interestingly, Osprey has redesigned the Stratos line for 2010. The Stratos 40 has been replaced by the Stratos 36 top-loader and the Stratos 34 panel-loader. The new packs lack the load lifter straps on the shoulder harness that the older design has - an important comfort feature. The new design will only carry one ice axe, which may not be too important to you. Of greater importance is that the older design will carry a water bladder in two locations, and will even carry TWO bladders simultaneously. I don't think that the new ones do that. The new designes are rated for a max load of 30 lbs and the older 40 liter design is rated for a max load of 35 lbs.
These things being so, I jumped at the chance to buy the older 40 liter model. Got a discount on it from BackCountry.com, too! To do that you'll need to either call or use the chat feature. These are good folks and they'll work with you.