I haven’t purchased anything from UP, T sport, EVT, MPP, etc. I am only basing my info from what I have seen posted on TMC.
I have been following most of the threads about performances parts on this site. It seems to me that they are a good company to work with. I would only buy parts from aftermarket companies if the parts are in stock. When people buy parts in development or back order they sometimes get disappointed.
UP stands by their products but sometimes people complain about their communication. I think some emails fall through the cracks. People will post complaints here and their problems get rectified immediately according to follow up posts.