This bike, I class as the little brother to the beast of bikes the R1(see review). Having only ridden this bike for 4 hours, it was clear to see why this bike was made.
I currently ride a 98 zx6r and in comparison there are subtle differences. The zx6 was crowned king of 600 class 98/99 even though the most popular bike was the CBR(suprise, suprise). Yamaha had to release something that would strip the kawazaki and beat the sales of the CBR.
The first thing noticeable is the riding position. Yam have favoured the more comfortable CBR trait, rather than a lower racing position.
The styling is obviously in the vein of the R1 and other manaufacturesr have copied (ie fox-eye styling on the new kwak), but styling and ride position would not be enough to beat the kwak or the GSX really.
The engine in the R6 is very responsive, even though best results come, when you hold the the throttle in the red. It handles reasonably well and overall is a good bike.
I think for the 600 class its a tough call between the 2000 zx6 and the R6. I think too may people are getting carried away with the fact that the R1 is ultimately the best bike around and so it must be true of the R6. The differences are monumental.
The 750's are no longer a stepping stone to the big bikes with the ZX / GSX and R6 offering similar performance to some of the 900's.