My one experience with KEH was very positive. I found a used 24-120 F3.5 for an insanely low price rated E. It came with caps and hood and was in great condition and still working fine after about four months.
I'll grant you I dont have a fifty inch monitor and I dont pixel peep but it seems to get along just fine with my beautiful D 700.
BTW their packaging was superb, double wrapped securely in thick bubble wrap with two sizes of bubbles and arrived exactly on the day they said it would.
I was going to buy my new 17-35 from them but they sold the last one the day before my cc payment cleared.