A definite +1 for the SKS Chromoplastics (now called P35/P45 depending on the width) I got a set for my commuter and they were easy to set up and look great on a classic steel frame, which is unusual for plastic guards. They were $73 delivered from CRC
Whilst the Topeak Super Tourist is a great rack, after a couple of years use I've cooled a bit on the MTX DXP (? .. it's the biggest one) TrunkBag. At least in my experience I've found that except for the odd occassion here and there I just don't want to take my panniers off and carry an awkward shaped sort-of-bag in that doesn't stand up by itself and won't balance properly when you walk with them.
Like some of the other posters I generally keep some cotton shopping bags with my clothes and shoes in them in the panniers, and take those out to go into work. My bike clothes get hung up at work, and then I change and my work clothes go back into the bags to be carried to the bike and home.
There are better panniers out there that are easier to use and get your stuff into (it can be a bit of a squeeze getting size 13 shoes into the side panniers) if you are prepared to leave them on the bike most of the time, which has turned out to be the case with my Topeak panniers.