I use a lot of SD cards in my work with embedded Linux applications. I have had the opportunity to use many vendors cards in our systems.
That being said, PNY cards are some of the worst, and I have tried every major brand and most minor and "no-name" brands as well. Also, I am not talking about buying a card or two here or there, a small purchase is 20 cards.
We now use Sandisk UltraII and ExtremeIII cards exclusively. I have even changed our warranty statement to require those cards. These are systems that are priced somewhere north of a new 50 mega pixel medium format kit, that perform mission critical functions (Mistakes costs millions, if not lives) so we do not make these choices casually.