Since I'll be riding farther I won't be doing it on the upright, which means I won't be wearing my work clothes. To make transporting my duds a little easier I ordered the garment bag fromTwoWheel Gear. The short version is that the bag is a full length garment bag which hooks to bike racks like normal panniers. I don't need to carry much other than some papers with me, and the bag has plenty of pockets for various things.
In the upper picture you can see the non drive-side of the bag, which has most of the external zipped pockets on it. The bag also has a zipped pocket on the top in the section that sits on top of the rack. The bag has two types of handles with shorter carry handles as well as an adjustable shoulder strap. Also, clearly visible in the pic are the day/night-glo strips on the rear of the bag. The reflectiveness of the strips is more evident in the lower pic. Also visible there are the angled hooks for attaching to the bike rack.
I just got the bag and haven't been able to test it yet, but once I have I'll write it up.