I consider KEH as an honest business. That said, they do make mistakes every now and then and I had a few instances where it took a while to get it right. But, all through the process, they were courteous, understanding, and in the end, things were righted. One time, I was treated rather curtly over the phone but it was just one incident. Perhaps that particular rep was having a bad day.
Buying used anything, having a reliable business on the other end is worth more than a little saving for me. Like anything, opinion varies all over the place depending on individual experiences. I continue to buy from KEH.
Concerning ratings, it range from conservative to about-right depending on the piece. Would they deal on prices? Probably not but never hurt to ask. All they can say is no.