I just purchase a Bronica GS-1 back from them and am happy with it. I still have to run some film through to check for leaks, though.
I think places like KEH are fairly consistent in grading items. Once you get a feel for their system, you pretty much know what you will be getting. The same can't be said of random sellers on ebay - they can have different ideas of what "Excellent" or "Fair" are.