I ordered a set of Planet Bike Freddy Fenders Hardcore from Bike Nashbar (and then promptly found them for cheaper on Amazon.com, but so is life). They are located in West Virginia, but the stuff they sent me started in Ohio so they came overnight. I put them on Friday night and naturally we haven't had any rain yet, so I haven't had to test them. I suppose it's something like remembering to bring your umbrella being the best way to make sure it doesn't rain.
I was impressed with how easily they went on - I had to rummage around in my box of random screws to find ones that matched up for my front fork, as the ones they sent weren't quite long enough to go through the fender's attachment and my fork, but they back one worked fine. I'm looking forward to seeing how these work.