They're basically like any plastic fender, except longer with built in mud flaps. They have a lot of ups and downs. First, the coverage is probably better than any fender I've had--better even than VO's fluted 45mm fenders [I think the longest one they sell.] Perhaps if I had added flaps to those, I could out-do these SKS's. Like most plastic fenders I've installed, they're pretty easy to put on. They're also pretty light weight, for what its worth. Oh, and they make my 65Ob'ed 65cm roadie look not crazy weird.
Front fender ground clearance.
But that's about all the good I could say about them. First off, there is the basic flaw of plastic fenders in that the edges of the fender aren't curled around allowing water to spray out laterally from the bike, which invariably goes back a little and gets you slightly damper. Metal fenders of a decent quality always go this going for them. The extra long design also doesn't translate well for plastic, as the amount of flex these experience is notable. Luckily I have a fair amount of clearance for my 32mm tires, but if I hadn't much room to spare, I could see these rattling against the wheel. Actually now that I think about it, the dirt road to my house causes the fender to slap against the tire side wall...
Looking at the photo above, the fender comes extremely close to the ground. What ends up happening is that the flap acts like a funnel for debris to get caught into. This happens a lot. Like crazy amounts. Maybe if I road strictly on clean roads I could avoid this, but fuuuuck that. Rivendell now sells this remedy for their ill-fated design, if you can ignore the other short comings.
The fenders also are a pain when trying to make the bike smaller for travel, but that's pretty much any fender of this coverage.