I had one on my 99. Not a really loud pipe, which is what I wanted at the time. My bike dyno'd 131 hp with just the slipon. I think its a nice looking pipe. I've still got it around somewhere if you're looking for one. I took it off to go with a full system.
1999 R1, Marchesini rims, RAM S/S swingarm, custom Hindle undertail exhaust, Ohlins shock and steering damper, race tech forks, Attack rearsets.
2000 R6, Full Akro exhaust, Ohlins shock, Daytona Damper, vortex rearsets and clipons.