I put these on the front of mine now that it's doing a serious amount of miles...after having a Focus that looked like it had been sandblasted on the front of the rear arches from stones thrown up off the front wheels, I decided I'd always have some form of protection on my cars!
Plus being Carbon Grey they aren't very noticeable...not sure what they would look like on a CW car though...
With regards to keeping the car clean...yes dirt from wet roads still gets on the car. But thick mud from gutters, country roads, and stones/tar don't get onto the doors anymore. I would prefer the looks without them on, but on the whole I think it's a good idea to have them on 
http://www.vwgolf.net.au/showthread.php?4101-Golf-R-Mini-Mud-Flaps
Dave, that's exactly why I have them on my car, and have had them on all my previous cars. Agree that on a Carbon Grey car, you don't really notice them.
