I've got a Timbuk2 medium and a small, I'm not a large person. I use them both, will load one up and come home, drop it off and grab the smaller one and head out for more cruising around, errends, shopping etc. If I were carrying serious papers etc I'd wish for the medium at all times at least, or the large and to be a lerger person too lol.

Cheap wine inspiraration (I can't ****ing spell with this stuff on board but I do come up with some neat ideas) something I'd call a "spider", something really slick 'n' quick to latch into a standard uuuuugly Blackburn type rack, easy to load up and carry that way but easy to grab and take up into the office building etc with you so no stealie. Maybe I'm just thinking of something that's easily done with a well designed pannier and yes the hardcore commuters around here I'm in awe of are often seen with one pannier. Hic. I'm not sure I trust this stuff with that plastic cork.