That 4GB card is actually kind of crappy. I wouldn't waste your money. It's not an SDHC spec card, and for it to be a certified Secure Digital card, it must conform to the SDHC spec if it's over 2GB. There's no guarantee that it'll actually work in any device that supports SD/SDHC.
Nah, I'll be honest, I haven't. But at the same time, I'm not about to stop at the streetcorner vendor in NYC and buy a "Guccci" bag and see if the Manhattan socialites will fail to notice that I'm pulling one over on them with my knockoff
All that, however, is just my $0.02, so take it for what you will.
I agree its probably gonna be crappy for the 4GB, but hey $29.99/Free ship for 4GB.. I just cant complain =) I am not going to expect it to be a top performer but I am sure it might pass with alot of folks out there that just want extra storage on the go.