We added a set of Weathertech Floor Liners (a smaller version of the mats) a few months after getting our Odyssey, and I have to say they are the best mats I've ever owned. Made for the Odyssey, very heavy duty, and designed to catch water and debris like few others.
They're expensive, but well worth it. We tried some cheapo mats from Wal-Mart for awhile but they were practically useless.
Check them out:
http://www.weathertech.com/store/mvp...=281&Year=2007
(Sounds like an ad, but I'm just a customer - very satisfied one!)