I can confirm back packs suck. +1 Messenger. However. They can still make your back sweaty.

a lot of people here LOVE their racks and panniers. I guess I'd be more open to them if I had more than one nice bike.

For me, I'd rather ride my nicest bike every day than a beater. I want to be comfortable, and I want the bike to perform well. I mean, I use it everyday.

This means, the bike I use for Commuting and the Bike I use for recreational road riding are one in the same. And if I am out on a recreational ride, I don't want the bulkiness of the Panniers. So a Messenger bag makes sense to me.