I have ran Driven, Woodcraft, Vortex, Gilles, and a couple of knock off brand rearsets over the years. I have Gilles on the R1, because of the easy adjustments of them, with one bolt adjust for track, higher and back, and for a bit more comfort on the street bring them down. The biggest issue has been mentioned, and that's replacement parts. Damaged the brake side is a parking lot crash during the total control riding clinic doing 2nd gear circles, where I had my knee on the ground and the back end washed out, so slow and controlled, I had time to kill the bike with the kill switch and turn off the key as I was sliding. It damaged the footpeg and bent the brake arm, put a small scratch in the lower, about he size of a pinky nail, and scuffed the frame slider. Took about 2 weeks to get the replacement parts, but they are available, just not like Woodcraft, where almost all parts an interchangeable, and if someone at the track has a spare, you can usually swap it over.
If I was racing or spending more time on the track, Woodcraft all the way. If you want some adjustments just for more clearance, any will work, just look at how easy (and cheap) replacement parts are going to be. For the Woodcraft I had on my GSXR750, I had a spare foot peg, spare toe peg, and spare arm. Although I hammered out the brake lever arm three times, so I didn't really need it.
But to me in terms of looks and adjustments, I have loved my Gilles rearsets.