I've got some PNY SD and SDHC cards, a couple PNY thumb drives and some PNY RAM and haven't had a problem with any of it (yet at least). Neither the systems department I work for, nor I, think of PNY as a "cheap" brand or a brand to avoid. The "class 4" might give you some problems in some devices but I'd be surprised.
I have read about some devices having problems with SDHC cards over 4GB but not any particular brand over another. Read the threads on the board about the new Edirol R-44 as an example. There have been several reports of problems in that area but I don't know if it is a recorder problem or a SDHC chip problem yet.