I had STM on my previous RR-7. I do a lot of track riding and found it to be a big help. Under hard braking into a corner I found the bike was far less prone to the rear wheel locking up through engine braking. As a result my corner entry was therefore quicker and it made direction changing easier. The other thing I noticed was the because it was lighter than the OEM clutch the engine would spin up more freely. I would like to fit one to my latest RR but they are expensive so I'm not in any rush to purchase one. If you go anywhere near a track its a worthwhile investment. The two main manufacturers are STM and Sigma and vendors on here will be able to source one for you and confirm prices.
Slipper IMO is a MUST HAVE! The single best mod I ever did to my 07 600!
Keep the bike inline under hard braking
Allows you to focus more on corner entry
Keeps the rear from hopping allowing you to actually hit your turn in points, without waiting for the bike to settle
You can downshift latter, deeper in a corner, even after initiating your turn in
Much easier to match revs
And I'm sure I'm leaving some out.
"at 8k i often get the tire to slip a bit(kinda like stoner in motogp) when i start to get on the throttle"
As far as slippers being lighter than OEM not so sure about that. Both STM and Yoyo use stock clutch pack. With the added ramp mechanism to limit the back torque its hard to gain any weight savings over the OEM hub.
some track duty here.. i can't tell you how many times my rear tire bounced yesterday from not quite matching r3vs a few times yesterday at Sonoma Raceway (Infineon/Sears Point). Gonna try to find a good deal on a slipper for christmas and make my friends jealous.