I view KEH as the source of first resort for used gear. And certainly if it's graded EX+ it should be pretty nice. They aren't perfect - I once got a 135/f2 from them that proved to have a bent lens mount, but they certainly took care of the problem painlessly. I wouldn't pay more (or even equal) for used gear anywhere else unless I know the seller quite well.
Their BGN gear is usually just that: great value, although you can usually expect that BGN stuff looks like it's been used. Chances are that an EX+ item will visually appear to be new or just about new, missing only the original packaging and possibly with some dust.
Do note that in addition to the 14-day no hassle return, you get a 6-month warranty. I bought a flash from them earlier this year and it had an intermittent problem which in the end was a loose wire. (But I sure couldn't tell that.) I was without the unit for a week or ten days, but it's been 100% reliable ever since.
I've bought MANY times from KEH. Far too many, according to the CFO...
_____ Brian... a bicoastal Nikonian and Team Member
My gallery is online. Comments and critique welcomed any time!