My original clutch started noticeably slipping around 20k miles...whenever you got into boost in 1st,2nd,3rd the motor would rev up faster than the bike picked up speed. It got worse very quickly....from only on hard pulls in 2nd, to just roll-ons in 3rd. Within maybe 500 miles it went from slight annoyance to major issue...couldn't get on the gas at all without it slipping.
I got the PCW kit, which was like $150. Comes with a set of OE Yamaha friction plates, an extra (eigth? iirc) friction to replace the half disc, their heavier spring, a new cover gasket, and directions(bah! who needs em)
Tossed the anti-chatter thing in the back, replaced it with a friction, lightly sanded all the pressure plates, dipped all the frictions in oil before installing, and made the clutch sandwich. The spring fit like OE and everything went together smoothly. No more slipping. Granted, I have a stock motor, so built up ones might need more, but clutch response is night and day better. Dumping the clutch now gives instant burnouts and/or wheelies, where before I could never seem to get the front end off the ground.
The lever pull is supposedly a few lbs heavier than stock. I only notice it if I'm creeping along in traffic and constantly pulling it in and out, and even then it's no big deal. Plus the "feel" of the clutch is pretty much unchanged. Heard the Barnett kit could be kind of "grabby" and annoying to handle around town.
I have a venture drive as well...which probably causes a bit more wear from it slipping a bit more to get going in first.