For anyone who's considering the bike commute but thinking "I will sweat so much!" do check out panniers. The OP says he only likes panniers for grocery shopping, and it's true a lot of panniers are basically buckets you strap to the back of your bike. But Arkel, a Canadian company, makes:

* a pannier that turns into a backpack

* a pannier that turns into a briefcase (though their new design isn't as conservative as the old one)

* panniers that actually works as shopping bags with handles

as well as a full line of touring and camping panniers. And their customer service is good -- over the last 12 years I had a zipper and a strap repaired on them.

I like commuting a lot more when I don't have stuff on my back -- it feels like it makes me more agile on the bike.