I just started using a pair of Ortlieb back rollers for commuting myself... the mechanism for attaching to the rack itself Just Works. It's fantastic.

So far, the snow/salt season has not affected the items in my panniers at all. My professional clothing actually looks better than those who drove, as they had to walk a block in the nasty weather from our parking garage!

I've found myself only using one of the panniers (on the right side). Aside from some low-speed wobbliness I've felt no difference.

REI's got 'em on sale right now. To me they were worth the spend, as I like luggage that threatens to outlive me.