I've had nothing but great service from all LF retailers I've purchased from.
MPEX is great: They sold me a new lens for just over the price of the same one used, when the used one had already been sold and not removed from their web site.
Badger Graphic is great: They sent me a custom ordered lens without a credit card - they just included the bill with the shipment.
Quality Camera is also great: I custom ordered a grey market lens from them and when it arrived at their shop they called to let me know that they were charging me $100 less than the already aggreed upon low price, due to an improved exchange rate.
I haven't met a nicer and more super honest bunch of people than those involved in LF photography.