A backpack beats rack and panniers for me. I use a good quality internal frame backpack loaded to 24 pounds on my commute of 13 miles one way. This pack is beautiful on weekend trips skiing in the backcountry with 45-50 pounds, so 24 pounds for 45-50 minutes is cake. I imagine that 24 pounds in a basic school-type backpack would be miserable.

I tried rack and panniers for two weeks earlier this year but returned to the backpack because:

- With the pack, I'm just a heavier rider. Put that same weight in panniers, and my light and agile trail bike turns sluggish and unresponsive -- much less fun on my mixed trail/road commute.

- I do get a sweaty back, and often sweaty shoulders and waist to boot. But I still get sweaty, pack or no, regardless of the temperature, so I have to change when I hit the office regardless.

- I always carry a notebook computer, and often other somewhat fragile items. In the panniers, thinks get kicked around pretty good. In the pack, things are protected by the human shock absorber.

There are times when the backpack is the wrong size for what I need to haul. For bigger loads like grocery shopping I use a Yak trailer, which can carry 2x the volume of both rear panniers. For smaller loads, I use a Mountainsmith lumbar pack that can carry as much as a basic rack trunk.