VegasChick wrote a review of Osprey Packs Sirrus 36 Backpack - 2100-2300cu in - Women's on March 28, 2011
With 20 lbs of gear and 3L bladder, I took this pack out for an 8 mile hike in Red Rock Canyon on a Friday then again Saturday. Friday found me hiking in snow flurries and 40 mph winds in the desert. This pack fits my small torso perfectly, does not shift around as I jog downhills or reach down to boulder. Saturday was sunny and relatively hot in comparison. The air speed mesh back kept me cool, I almost didn't want to take off the pack on my rest stop. The 2 waist belt pockets are difficult to unzip and zip yet handy for energy packets. Shoulder strap pocket is tight fit for cellphone.
I found myself having to retighten shoulder straps every 2-3 miles.
Includes integrated Osprey raincover. 3L bladder pocket inside or 2L can be squeezed in between mesh and pack. I may use this to hold additional water when climbing Mt. Charleston 12k; 18 mile roundtrip 4,500 ft gain with NO available water. 2 side mesh pockets to hold sweaty socks or frozen water bottle (think desert).
This is going to be my go to pack for extreme dayhikes and overnighters. Not too keen on color but who can see their pack when hiking?