I've gone through 4 of the pirellie pro scorpion rears to my one pro scorpion front. I like the front and it has lasted a little while but I really try to stay off of the front brake on road.
The rears stick something fierce but the last me about 300 miles before they are so worn they start to suck off road. Maxxis makes a desert type tire that I am thinking of trying since it is tougher. The rocks around here seem to chew up the tires and I am hoping that might help that it is a desert tire... That and it was suggested to me by a friend who rides around boulder a lot.
Interestingly, I had a 606 sitting around that I threw in the 525 while my brother was in town and it did better than the worn out scorpion pulled off. It has worn great also.. Only reason I am tempted to go with the desert maxxis tire is that I am hoping it performs better than the 606 without lugs ripping off like the scorpion. That 606 rear kinda sucks on slimy trails too.
Fwiw, the crf230f has a 606 on the front with some other no name rear tire and my mom washed out on it and crashed a few weeks ago while she was here. No real damage to her, but I think it speaks a bit for that front tire. Not necessarily the best front out there.