so far the card has been absolutely solid. Given that SDHC is likely to cause the disappearance of non-SDHC 4GB cards, I would definitely make sure I had more than one as it might be a while before we see Cacko module for SDHC.
Fortunately my wife saw my "amazon wishlist" and also got a 4GB for my birthday, so now I am awash with cards!
Having all the extra space is really useful, much faster to blast files onto a card in the PC's usb2 card reader then put in Z than using pc-to-Z tcp/usb, or wireless.