I have yet to have a bad transaction with any vendor as of yet. Not to say the bad vendors are not out there.
Some are slower to respond than others, but all have responded in a timely manner...even if it was not on my "perfect" schedule.
RandyT at GGG has been more than helpful and responsive to my queries. Yes sometimes it takes him more than a few hours to answer (sarcasm here) but he has always answered and provided the tech support I need to fully enjoy his products.
Divemaster and Ponyboy have been very easy to deal with.
I even got my t-mold from Dream Arcades and had a great experience there.
I think some forget that these people provide a service to the home arcade community. With very few exceptions, THIS IS NOT THEIR JOB! It is a sideline service for a niche market. Given the circumstances, I think they do an outstanding job overall. They provide good quality products, reasonable prices, get it to you relatively fast, and provide free tech support!
No quams here, but your experience may be different than mine.
Xam