I have to say that for my money the original rear guard was the best by far. I'm sure it would still work on quite a few full suss designs as it sits close to the tyre and could be made to follow the wheel.
I modified the 2 I had. I like to be able to remove a rear guard in good weather for aesthetics (oh how we laughed!). I used to cut out the cross piece that had the fitting to the seatstay bridge. I then melted a hole in the two side "struts" that were left, and then simply zip tied to the seat stays.
I'd buy one.
My Crud Guard fetched me off on the road last week though. Some how it got in the way of the fork preventing me turning sharp right off the road on to a track. Hit the tarmac like a bag of spuds dropped from an airship! Oooh it hurt for a while.