I just had a 2nd hand (1500 miles) STM 48 tooth slipper. It sounds much better but then a 1500 mile standard clutch would sound similar. I suspect it will wear better though.
My reason for wanting it was that I was locking the rear wheel on downshifts (on the track, not the road). As my braking got later and corner entry speed increased, I found I got worse at downshifting in time to be in the right gear for the exit! I was coing out in a high gear, having slipped the clutch in whilst in the turn (as KeefyB noticed in a recent photo!). Yesterday I tried it at Cadwell and whilst it takes a little "getting your head around" to learn to just drop into gear and not worry (too much) about feathering in the clutch, I noticed I was getting better at getting in the right gear for a fast exit.
That is until the bike packed up and becames a 375cc single.
[Edited on 20-9-2005 by HW]