I have Andra CSS rims on my Robert Beckman touring bike. I was in Oregon this Spring, and coming down big hills in the pouring rain with a touring load was frightening. I've switched from SwissStop blue to Koolstop pads, which I think are better, but I haven't actually encountered the identical conditions, so am not sure.
My Nomad Mk2 actually has the CSS rear, non-CSS front recommended by Andy (not by plan, we simply couldn't get an appropriately drilled front rim -- I waited 2.5 months, and then had them build it up non-CSS).