The ZX12R was the joint fastest production bike along with the Hayabusa up until the ne ZZR1400 came out at the end of 2005. It puts out 160 odd horsepower at the wheel straight out of the box and has massive torque all through the rev range to match.
Although this is a portly looking bike the handling is surprisingly good once the suspension is sorted and set up. With a brave and skillful pilot it can keep up with the latest crop of 1000cc sportsbikes on all but the twistiest of roads. You have to be brave though, go into a corner fast on a closed throttle and that massive weight will push the front tyre quickly into the verge. Get on the gas with more than the merest whiff of throttle while banked over and the rear will instantly spin up. Picking exact lines and using perfect throttle control has never been so important.
On the track it's a different story, the 12 struggles to keep with 600's let alone 1000's. Spinning out of corners onto the straight hinders progress as the smaller bikes get the power down without having a bus like projectile to shove along. Coming up to corners at similar speeds to modern 1000's is even worst as the brakes overheat causing the lever to come back to the bar (and thats if your lucky enough not to lock the front) as the front tyre is overwhelmed by sheer force.
Sticky rubber may solve the problems a bit but with rears lasting 1500miles if your lucky and brake pads about 2 track days this bike is just to heavy for anything other than road use.
Stability is rock like though, even flat out over bumps the chasis never does enough to scare. Wheelies are awsome as in 100mph launch speeds but care is needed as it's easy to flip when approaching the balance point. Landings are often hard and as a result fork seals and headrace bearings don't last long.
To sum up the ZX12R is an ace bike, the type that everyone should own once, but only for a little while. Wear and tear is phenominal, it drinks as much fuel as a fast family car, and destroys consumables like their going out of fashion. It has an amazing motor that has to be abused to be believed and it makes a good tourer (take a jerry can and spare back tyre).
On the down side it is fat and ugly and no matter how good the ride is I like a nice fire place around my fire. Buy an early unrestricted one for 3 grand off a rich old guy, abuse the hell out of it for a couple of months and get rid before it costs you.