I have the Nashbar ATB panniers. For touring they get the job done, but for commuting, I don't know. I find that what I didn't like about them is that it took some fiddling to get them solidly fixed on my rack. Then if I had to take them off for any reason, the process started over the next time I put them on. Touring: no big deal. Put them on and leave them on. Do all your fiddling/fine tuning during the first half day of riding (during which I have to check them because one always comes halfway unhooked), then they're good for the rest of the trip. For commuting, if I was taking them on and off the bike, I think they'd drive me crazy.

For 'round town errands I am a big fan of "grocery bag" panniers. I think I may also have an REI set. They lack the extra velcro loop that holds the Nashbar panniers in place, but even so, they seem to stay put better. Just use whatever bag/backpack you want and toss it in the pannier. The other day I saw a set, by Soma, I think, that had hooks that grabbed on to the rack like the better panniers do. If my old set weren't working just fine, I'd be considering upgrading just for the attachment system.