Some of us have been using the Transcend 4GB cards for 24 bit recording. If you are running 16 bit you can maybe go with a little cheaper one. Just don't buy anything off ebay unless it's a seller you already know and trust. There is a flood of cheapo imitation flash on there. They even go so far as to put an official looking sticker on the card.
Formatting the card has as much or more effect on write speed. Use a 32KB allocation table.