Make sure you don't plug your 4gb transcend into your pcmcia port to copy over files as this is how i damaged my 4gb transcend. I would not use cf card over 2gb on pcmcia, although some ppl report greater stablity with sandisk cf cards.
I have both sandisk and transcend cf and i think the quality is similar between the two.
(Actually i think you're better off with a proper 4gb or 6gb hd rather than a cf for longer term stability but others will always disagree...)
