Have to agree with you on the Rack - Panniers set-up. I used a Topeak rack and MTX Trunk Bag with Panniers on my hybrid and thought it was the bees knees. Then following the rule of N+1, I picked up a Tricross Comp a few years back and was amazed at how light and quick a bike could be. I went with various types of backpacks, messenger bags to try and keep the bike light and sporty, but finally broke down and mounted the rack and Trunk Bag on the Tricross. Carrying a messenger bag was ok, but when I added the U-lock and cable, it was like throwing a brick into the bag.

My commute is totally flat, so the panniers really don't slow me down too much. You have to carry your stuff anyways, and for me, I'd rather have the bike do it than my back.