I bought this card to use in my Canon EOS 50D and it has worked perfectly so far with no problems at all.
It is fast enough to take a burst of shots on the jpeg + Raw setting @ 6.3 frames per second with no loss of speed that I could detect, even on longer bursts.
Read speed is also fast as it only takes a short time to download a large number of jpeg + raw files direct from the camera onto the PC via the camera`s own usb cable, with no read/write errors so far. (It may be faster still with a card reader)
I have been using the 16gb version of this card on my other camera body (EOS 40d) and I was so impressed with the cards performance that I bought this 32gb for the higher resolution EOS 50D. and this card does not disappoint either.
With the camera set on jpeg and raw image recording, both on the highest resolution possible, (15mp) you can still get over a thousand images on this card, thats about 4,000+ high quality 15mp jpegs on one card, and on a 10mp camera about 50% more than that. (although this does vary depending on the type of pictures you are taking, as some pictures contain more information than others and have a larger file size.)
Please remember that not all camera`s, (especially older models) are compatible with high capacity CF cards, check your camera for compatibility before buying this card to avoid any disappointment.
All in all this is an excellent card that does everything the manufacturers claim, and it does it well.