I finally scored a set of Nissin calipers that have gone onto my 05 636. They came off a 2007 ZX6R. Holy crap are these calipers so much better than the stock Tokico ones!! The lever is rock solid right away, something I was never able to get the Tokicos to do, regardless of how much bleeding or other tricks I tried. They always required more pull to start engaging, enough that I had the Pazzo brake lever adjusted out to 5 which is the furthest from the bar. With the Nissins, I was able to adjust the lever closer, down to the 3 position. Full braking comes on much faster now and is still predictable.
I have discovered now is that I seem to have warped rotors, something I never really noticed with the Tokicos for some reason. I know for a fact the Nissins didn't cause it because I could feel it the very first time I applied the brakes. Its not too bad tho so I will live with it for a while until I can either afford Galfer rotors or find a new set of stockers on ebay.
One thing I really noticed while doing the swap and cleaning up the Nissin is how much better the build and finish quality is over the Tokicos. The Tokicos look carved out of a brick while the Nissins are a sculpted work of art.
If you are looking for an affordable brake upgrade, this is THE way to go. The Nissin calipers are fantastic! You can find the Nissin calipers on 2007/2008 ZX6Rs, 06/07/08 ZX14, 08 Concourse and on the 07/08 Z1000. These are a direct bolt on modification and I would HIGHLY recommend adding Galfer or similar brand braided brake lines with them if you haven't already. The standard 05/06 Galfer lines I already had work just fine with only a couple extra inches of slack in them now.
Before with the stock tokico calipers:
After with the 2007 ZX6R Nissin calipers:
My 05 with 07 front and rear brakes and 06 ZX6RR forks and rear shock: