The 9 is comfortable for short-medium (<150 miles) distance. I have a set of helis I need to put on it. The seat is the worst part, but pretty much all the bikes have shitty seats and I have a plan to try some different tricks to see if I can make the seat more comfortable. Passenger seat I might be able to upgrade - my wife and I went for about a 60 mile ride the other night and she is complaining of being sore. She just needs more saddle-time.
As far as the track goes, I've never had another bike on the track on than the ZX-9, which, weight-wise, compares favorable to the 93 CBR F2 I had. I honestly have no complaints about it at the track. At this point, it isn't the motorcycle that is holding me back, it is just me.
I have considered the ZX-12. Similar but a little better ergos for both passenger and pilot. And a bunch more power.
Mostly, I just got bitten by the 'new-bike bug'. I'm slowly working it out of my system, though.