As for speed, the difference when copying to your computer can be drastic. A fast card can transfer a gig in just over a minute and a half (I'm talking practically here, not theoretically), whereas a slow card may take 5-6 minutes. If you're copying on USB 1.0 or using a non-CardBus PC card adapter (the $10 ones as opposed to the $40 ones), you're looking at closer to 15 minutes per gigabyte. That's 7 minutes per 4 GB instead of an hour.
Fast cards are worth every penny, especially these days -- fast 2GB and 4GB cards are all relatively inexpensive.
So which way is the true fastest way to get images off of CF the ExtremeFirewire? Does this need a different 1394 port on your computer? Anybody know?