I personally have not. However, a friend of the family had a YZ450 with a Scotts and a KTM 450 EXC with a GPR and he said the Scotts was superior. I have dealt with the staff at Scotts for many years and their customer service is great. Once, my damper had a little bit of black grease near the top of the armature, nothing major at all. I called them up and they rebuilt it for me at no charge.
I think I will go for the scotts bolt on kit(above the handlebars) then. I have only heard great things about scotts products and customer service.
On their website they only show kits for the 06-07 bike. Will these fit the 08 with the shorter headtube? Or is there a special kit for the 08?