The few times I've had to deal with them, they've always been kind to and worked with me. {knock on wood!} The receptionist is particularly friendly and warm when I've called.
However, I just today messed up a shop due to a major brain-fart. I sent an explanatory email owning up to it and how stupid I feel about it, apologizing profusely, and asking if I can re-do the shop in a couple of days. I will see what happens.
I too have done hundreds of successful shops for them, and as mentioned have always had positive interactions with them in the past the few times I've had to have one with them... *fingers crossed*!
BTW, this is the first shop I've ever messed up on like this, for any MSC! I feel really really stupid about now. *sigh!*
Practitioner of the Nerdly Arts.