I bought the 12 new in 07 in a model runout sale before the ZX 14 superseded it. 4 years of ownership, and it rates as the best all round road bike I have ever owned.
It's got monster power and torque right across the rev range. It's just so easy to leave long black lines out of corners, and murders rear tyres if you're heavy on throttle.
Handling is very stable at high speed, and it feels planted on the road. The bike is a heavy unit by modern standards, and this shows up in the tight stuff, but conversely the weight helps it at high speeds, it's rock solid and planted in big number bends.
The standard brake setup is disappointing, spongy with average stopping power, new pads are a must have on a bike this fast.
ZX-12R ownership makes it hard to keep your license intact.
Modifications are Power Commander III, K&N air filters, a Pipe Masters slip on, brake pads, braided stainless steel brake lines and a set of Helibars for comfort.
The old girl has just been dyno-ed at 175BHP at the rear tyre, which is not bad for a 50,000 klm plus bike.
The 12 is still a seriously fast bike 11 years after it first appeared. I think I'll keep mine for a little while longer yet.