Yeah I looked at the Oxford Stormex and Rainex and saw mixed reviews. The cover I have is just a basic PVC Nelson-Riggs econo. Sure, it keeps the water out (from above) but then traps it in either in condensation or who knows what.
I saw the Dowco--looked pretty good. If you leave the bike under it for a day or two do you find that there's any condensation built up?