I didn't really care which card I bought before joining the forum. I read that some new ones are faster and some are more reliable than others, but not until I started shooting more than 200 shots or more at events did the speed really made a difference. I have 2 4GB Extreme III's (one from Dante and Thanks), which I use exclusively on my 5D. Even with the 4GB, the transfer is fast, "WOW" fast and only takes 220-230 RAW + small JPEG on one card. That's painful if you only have 1 GB cards. I have 3 2 GB Ultra II's for my 20D, which is plenty, and 4 1 GB Ultra II's just in case. For the 5D, you really need at least 2 GB and the II's or III's or 133 speeds are by far the best. None of my cards have failed me (knock on wood), so I trust the Sandisk company for that. The speed of the capture is great, also speed to the computer for transfer is even faster with a good reader. Can't go wrong with the newer, faster Sandisks.