Hello,
I've been a KEH customer since they had a store in the Dallas area. I have purchased from them through their catalogue / email ever since. Most of my used gear comes from them. Great people and an incredible price and service. Their return policy is out of th is world - don't want it, send it back: no questions asked.
Don't know about their international sales, but I've never had a problem with them in all the years I've dealt with them. They have shipped items across country and across the world (a few to me here in Afghanistan). The only issue is that they only send out USPS (all I can receive over here) once a week and if you order after that, it will take two weeks to ship the item. As long as I know what day to expect it, that's no concern.
I have found their repair dept. to be more than adequate for Nikon and Leica repair.Once I bought a Leica M5 from them that had a loose battery compartment and they did an entire CLA / Repair on it for no charge. They did a repair on my Nikon F3HP which included structural repair / replacing a broken computer board for a very nominal fee. The camera still works like new 6 years later.
For new gear I always use B&H if I can - which is 99% of the time. My experience with their used dept. has been much less satisfactory than KEH's and after years of working with both, I avoid B&H used unless they have an item I simply cannot get anywhere else (there's a long story there and I won't go into it on a thread about KEH).
I would suggest that any "problems" with KEH come from one or the other of you not understanding the other's expectations. If you know what they want / need to do business, then there should be no conflict. If they know your expectations, they will tell you up front if they can or will meet them and then you must decide whether or not to do business with them. In the end they will be fair, even if they don't meet your expectations.
Jeff M