Others say...

"Used as a solid-state drive."
This CompactFlash was used in a CF-to-SATA converter and then was installed in a car computer. Previously I had tried a cheap $20 4GB memory chip but it was way to slow. After swapping it out for this one, the machine had become usable. I own a SSD in my laptop. This is obviously not as fast as that, but we did notice that with this memory chip the machine was quick enough for you to forget you're using Windows XP without a regular hard drive!

"Great Performance"
I debated between these and the III cards and decided to spend a bit more on the IV.

I have three of these cards so I can shoot all day if I am out and about (though usually shoot about 1-1/2 cards usually).

Each card has performed flawlessly and the speed is well worth it. I have some slower cards and they do not perform as well, which is especially noticable when shooting a sequence of shots, I can get more with these cards.

Of course the burst may not be something you need/require, but I prefer having it just in case. Also the download speeds to the computer does save time. Again it reallly depends if it is important to you. Usually it is not that important, just put any card in and walk away for a bit, but on the times when you are in a bit of a rush it is worthwhile.

Overall the little "would be nice to have" speed at certain times makes this card a good one.

"Fast Card but Worth the Extra Cost?"
I purchased this card in the hope that it would allow more shots to be taken in burst mode. I set up a Nikon D300 to shoot continuous mode, raw format, 12 bit depth, 1/500 second, f4 with auto ISO off, manual focus and made shots with Extreme IV, Extreme III 8 GB and Ultra II 4 GB cards. I made shots until the camera buffer filled and the shot rate paused. The Extreme IV allowed 19 shots, the Extreme III 18 and the Ultra II 16. I repeated the test 5 times with each card and got the same results. The only thing I found that affected the number of shots was file size. Dark subjects can be compressed more and as a consequence the buffer can hold more shots before the shot rate slows.

I used a SanDisk imagemate card reader to upload 200 shots to my computer from each of the cards. The Ultra II took 5 minutes 20 sec, the Extreme III took 4 minutes 5 seconds and the Extreme IV took 3 minutes 50 seconds. My card reader may not be fast enough to take full advantage of the Extreme IV read rate.

For me the additional one shot in continuous mode is not worth the price differential between Extreme III and IV. For ordinary shooting that doesn't involve continuous shooting in RAW mode, the Ultra II is good enough for me.

I have never had a problem with SanDisk cards the Extreme IV does come with recovery software. In my opinion it comes down to a question of whether or not the extra performance is worth the price differential.

"The Best"
When I first went to digital I tried several different cards, after about a year Every card besides SanDisk had errored. I have the Cannon EOS family of cameras that shoots between 8 and 21 megapixels, and have used the cards in all conditions from sand to extreme cold and have never had a problem. But they may all blow up tomorrow.SanDisk 4 GB Extreme IV CompactFlash Card ( SDCFX4-4096-901 )

"My 4GB San Disk"
So far, so good. I have just started using it and already have seen the difference. I put it in my mega bucks camera (which I stopped using) and voila!The San Disk 4 GB, made it all happed. The camera started performing like a camera should. Not so with the other memory chips.

Thank you