I cannot speak to Duraflap, but defer to the opinions of several respected here as to its quality. I have had experiences similar to Ed's, and our driveway/sidewalk/street interface is no mudflap friend, especially with the 2005-2006 and other model Montys with relatively low backsides. The thing can get trapped in dirt and gravel on uneven campsites, etc., or worse, asphalt. Getting caught between a hard surface and the hitch didn't ever help, but the Roadmaster hitch roller I finally added did. Since Henderson's tweaked the air system, I've had few if any episodes with dragging back there, so even a half inch or a more balanced coach overall can make a difference.
A couple of times I've put our mudflap on sawhorses and straightened bends, and touched up rusty spots with POR-15 paint. But scratches in the chrome just have to be accepted, and aren't too noticeable under the coach anyway.
Now I take the extra step to remove the flap when we get home and haul it 30 ft into the garage, storing it flat under our pickup. I just have to remember to put it back on when we start trips. The thing is heavy and cumbersome, hard to unhook and rehook by myself, and dirty, but unscathed from the driveway now. An advantage is that it's easier to scrub, check for and treat rust, and polish when it's out in the open, as opposed to fastened under the coach.
Joel