I love my packpack.

Does my back get a little sweaty on my 45min bicycle ride to work? Yep. But I change my shirt, have a spare deodorant in my desk (should I smell goat-like) and do a quick wipedown w/ a wet towel when I get in.

I really got it for motorcycle commuting years ago and it's wonderful for carrying lunch, coffee, change of clothes and my laptop. I don't really want extra bags on either bicycle or motorcycle.