These memory cards are awesome. I use this card in my Canon EOS 40D. I hate the fact that prosumer level cameras use Compact Flash, but at last this card makes that a little less of a pain.
You can spend a lot more to get an Ultra or Extreme from SanDisk that is still slower than this card. I would highly recommend getting these cards whenever you can, if you are in the market for a CF card. The 4gb and 8gb seem to be 2x the speed of the 1gb, 2gb and 16gb models, but I think that speed difference is hard to tell, as most cameras can't write that fast, and transfers are very fast with the 2gb version using USB 2.0.