Steve, I had not followed them much at first as they were too expensive when they came out and I already had a full arsenal of Extreme III's. But now as the price is decreasing, they are now on my radar screen. One good thing is that the Extreme IV's have a lower power consumption - that equals to longer battery life with some saying an increase from 400 shots per charge to 700 shots per charge on a D200. With the IV's you are not likely to have to wait for the buffer to empty and miss shots. Any delay on that will be because of the camera write speed not the speed of the card. But more likely the only time you will notice speed is the down load onto a computer. But probably only noticeable if you use a firewire reader. You also must determine if the IV's are compatible with your camera. My D2x was manufactured before the III's and the IV's and the literature does not mention III's or IV's. Of course lots of people have successfully used them on a D2x, so common knowledge they do work. But then the technical part comes in, because they are not officially acknowledged by some camera manufacturers as an approved card, if for some reason the card messes up the camera (it has been known to happen), some warranties may not cover the damage. Now, that the prices have come down, and since I want to upgrade a couple of my 1 gig cards, I will probably purchase a couple of 4 gig IV's. My main reason would be for the low power consumption, not because of the speed. The question then is how large. I stay with the smaller ones. Cards have been known to go bad, leaving you with lots of images lost. I avoid the larger cards. I would rather lose 100's rather than 1,000's of images if a card does go bad. And the larger cards seem to go bad at a higher rate than the smaller cards.
