I just dropped my 06 ZZR 1.5 inches in the rear so my wife could stand flat-footed at a stop. Used a set of lowering links from Diamond Powersports in the rear, and then adjusted the front forks so the geometry remained level. Not sure if I just don't understand the finer points of riding yet, but I have noticed NO difference at all in the ride handling since it has been dropped. Bike looks good, rides good, no problems at all!
Good luck, and happy riding -