Yes, I have carbon pipe protectors on 3 of my 500's. The street legal 04 KX500, the 08 KX500AF and the 97 CR500.
The AF bike I stalled sitting cross ways on a rock hill and fell down the hill. I managed to leap off from the bike and stay on my feet but it hit very hard on the pipe. Protector saved the pipe. A few years back I crashed the 04 before I did the street conversion. Had a helmet cam on at the time.
http://www.kxriders.com/forums/index.php/topic,2559.msg18247.html#msg18247Here's video with the crash at the end.
Then 2 weeks ago I had a hard fall on the CR500. I drove across the ditch going home from my parents house, about 4 miles from my house. It has concrete that was slimmey and down I went. Went down on the right side, put a big grind mark on the pipe protector. Bent the ASV brake lever almost making it touch at the pivot point. I called them and they said send it back and they will send me a new one. The left side grip stabbed me in the inside of my left thigh. About 2 inches from getting castrated. Twisted my (bad) right knee. Almost stopped me from going to the Arkansas Hillbilly Dual Sport ride, 4-1-10. I could not kick the dual sport K5 so I had to ride my KLR650. The thing is a pig compared to the K5. I will do a ride report soon so take a look.
Carbon fiber pipe protectors are a must on the big 2 strokes for sure. I run E- Line and they are pricey but so are pipes.