I just installed mine but havent had a chance for a ride until over Easter. I got some 2003 R1 forks off ebay, sent to Sean to respring. He sent over the forks, triple trees and bearings to make it work. The stock brakes and wheel (I already have radial tires) will fit up, he included the axel. I next need to get a fender, although I think he has a bracket that can make the stock fender work.
I have read that the OEM forks with springs and radial tires are the most cost efficient way to go, which is what I had previously run. However, I t-boned a car and the forks were slightly bent so decided to just do the USD instead of replacing the stock forks.