I just bought the Edirol R-09.
It seems that people have strange problems at times with the Transcend 4gb SD card (files often need to be played with to get into the computer, playback not work in the R-09 after the recording, etc)
Anyone try the A-Data 4gb in the R-09? [Sorry, forget this I read here that A-data are lousy cards]
http://www.newegg.com/Product/Product.asp?Item=N82E16820211319
What about the PQI 4gb SD?
http://www.newegg.com/Product/Product.asp?Item=N82E16820141037
The only issue that I'm aware of with the Transcend 4GB card is that it sometimes fails to write proper headers on wav files. In reality it is probably due to the fact the current R-09 firmware technically doesn't support 4GB cards, so I'd bet you would have similar issues with other cards.
As long as you format the card properly and frequnetly between shows you should be good to go with a Transcend card.