The problem with the SD card format is they have too many sub-formats. There is the generic Secure Digital format which I first used on my Palm m500 many years ago. Then the miniSD format and recently the microSD format formerly known as TransFlash. Within this are the new SDHC spec for high capacity cards. A card you buy now is not guaranteed to work in future devices. In my case a device I am using now requires a miniSD card, but if in the future I purchase a device that requires microSD cards than it would be obsolete.
It is fortunate that SanDisk release the microSD multi SD kit which costs only a few quid more than a vanilla microSD card (I paid around 1 quid for it two weeks ago). It comes with two adapters so that it could be used in any SD, miniSD and microSD slots. Wonderful as this provides the type of flexibility I require. So right now I am using a 2GB microSD card on a Nokia N80. I am planning to get a HTC Kaiser, which has a microSD slot, in the future so at least the card is future proof.