They are good to deal with from a customer service perspective and most of the time you receive lenses in the condition stated or better. However, I did receive an AIS lens listed in EX+ condition with a very stiff zoom ring, but we worked out an equitable solution that accounted for the needed repair. KEH is best used on older AIS lenses that you just can't find elsewhere.
If it is something newer that is still in production you might find a better deal on line. I recently looked at a LN Nikon 85mm f1.4D that started out at a decent price from them. Until I found out it did not come with lens caps, or the hood ($50 hood + $20 caps). KEH will nickel and dime you on those things, even if it is a $1000 lens, they will make you pay extra unless specifically stated as included.
So don't assume anything, even though all lenses should have lens caps. KEH won't take the time to replace them if the lens was sold to them without Nikon lens caps. I don't expect them to hunt down every hood or factory case, but at least state what came with the lens when new and what is now missing. Why make the customer tract those items down separately?
They also charge shipping and tax on used gear because they are a part of Amazon now. I found a better deal through B&H on a brand new lens with a five year warranty that included all the things that KEH charged extra for. So what started out as a good value turned out to not be, I could simply buy it new for less. It pays to shop around and add up the little things before turning over your credit card.