I've purchased from QSC several times in the past year without any problems whatsoever, and know a number of others who have as well.
I still think they're reliable, especially for tirz and sema. Are they perfect? Nope, but neither are 99.9% of the other Chinese suppliers. Every supplier is only as good as their most recent batch that tested well. QSC's consistency has improved a lot in the past year, and even though they've had some screwups along the way they are still a safer bet than most of these new suppliers popping up who nobody has ever heard of and who don't really have enough tests over time (or any tests at all) to prove their products imho. They are also one of the only suppliers who send everything out for testing on their own.
Anyone looking for hand-holding, warm and fuzzy feelings, being called "dear", "sweetie" and "friend", or expecting Amazon-like delivery and customer service should probably shop elsewhere.