OK, after looking at a bunch of Rainwise stations, I should back up and say I only occasionally see the wet bias problem.
Whereas with Davis VP2s, well, it's uncommon to find one that's accurate in the middle range of humidity (40-70%).
Also, to be fair, the Acurite Atlases listed on Wunderground may very well be other stations at this point since the "beta" test period ended, I believe, and the product has yet to be released.