I use the Lexar 8gb UDMA 300x as I had purchased them when I got the 50D which takes advantage of the UDMA. I always look for rebates. The last 2 I purchased (recently) they had a $60 rebate. So I got both for $100. Plus I alway reformat the card after transferring the files to the hard drive...to me it's easier and faster than deleting the files.