Over the last 2 years I mostly used my Trek 6500 MTB for commuting. I used a backpack to carry my clothes and supplies.

Recently I decided to use my Trek 520 for hot weather commuting. The rack allows me to put a decent sized pannier (one Arkel T42 rear bag) on it and keep my back a little drier.

The bike is fairly modified from stock. Deore LX cranks instead of 105. LX thumb shifters instead of Dura Ace barends. Flat bars with bar-ends instead of drops. Conti Top Touring Tires instead of Bontragers. Jannd Expedition rack instead of Trek. Trek saddle instead of Bontrager. And fenders, too. This photo's a couple months old. I had just returned from a two-day, 150-mile tour, where I caught a stick in the rear wheel and tore off the fender. I recently replaced that Planet Bike rear fender with a cheaper Zefal plastic fender.