I bought a few items from KEH, starting in 2004, mostly film related items. Below is a Canon AE-1 that was listed as "bargin" condition I think for $125. Came with the 50mm f/1.4 and was just what I was looking for. Not a great photo but it's in very good condition and don't think there any brassing or serious scratches.
I never thought about calling to view the items before but I did make a mistake in my purchase and they were very helpful to give me a refund. I saw a Sigma 14mm f/3.5 Canon EOS mount lens for $140 "bargin" rated. Just was looking for a Canon 15mm f/2.8 and this was a great price! Turns out after making the purchase I found that the lens is only working on the film cameras and not the digital cameras. Called to KEH and they said no problem, also offered to help with issues like this in the future. The lens was clearly used but still looked clean and didn't have any major issues.
My only problem is that they use generic item photos and sometimes vague descriptions. I like to see a showcase of some select cameras and multiple views, just to see what their standard ratings really look like. But so far, I'll agree with everyone else, they rate much higher than other shops.
Just this week I made another order for my first medium format camera, a complete outfit and it was rated "excellent" I'll find out how it is next week.