I've had the 1199 (2012), 1299S (2015), Panigale R (2015) now the V4S Corse. Each one has had incremental gains in performance/handling but its huge jump to the V4. It's a totally different riding experience and a totally different bike. I test rode the V4S several times on the freeway and through the streets and I did not think it was that much of a difference. After taking the V4S through some pretty spirited technical canyon runs in Malibu Canyons, and Ojai Canyons I decided I was wrong. I don't plan on tracking this bike If I decide to track again it would be the V4 or V4R with higher spring rate than the stock one.
1 Better Ergos - Easier to rest my chest on the tank, I feel there is more room and my arm extension to the grip are better. Maybe it's because I can get my butt back in the seat without sliding forward which causes me to sit up on the older models. I'm surprised more people are not commenting on the ergos more.
2) Power Band - wider power band throughout the whole rev range unlike the narrow power band of the 1199/1299 series. The bike accelerates quicker and its stupid fast.
3) Flicks/Turn in better than my 1199/1299 - The V4S is on par or better than the Panigale R. (R is so light it makes transitioning fun and effortless) they both feels like a 600. I suspect you can run lines like a 600 on the V4 on a track.
4) Better feel in the brakes. - It's more linear like the throttle you know what your getting when you twist it as in the brake you know what you are getting when you pull the lever back.
5) Sound - Its sound good with the stock exhaust but nothing sounds better than the 1299 with Akra full system. That just sound mean.
6) Heat - Feels like the 899/959. The heat nothing close to the 1199 and 1299. I rode yesterday in 103 degree F in stop and go traffic wearing Dianese Drake textile pants and Cycle Gear heat out base layer and I had no problems at all. On the older models I had to put thermotec tape under the seat, carbon exhaust heat shield, Carbon frame covers and Carbon Fiber engine covers to reduce the heat in traffic. Although the CF looked sweet!
Its an Awesome bike I don't think you will be disappointed if you decide to upgrade.