A few weeks ago I finally switched to RAW on the CF card and JPG on the SD card. This doesn't slow down the shot rate (RAW to both would), but it at least gives me a JPG if the CF card fails mid-use. It means I have to empty two cards whenever I take the RAWs off the camera, but it's not a huge deal of extra work. The original reason for not doing that (and I've been not doing it for a couple of years), was that I wanted to force myself to learn how to process the RAW files, and while I was getting RAW+JPG I was always tempted to store them both, and keep looking at the JPGs. So I turned off JPGs totally, and spent two years getting comfortable enough with RAW files that now when I get the RAWs off, I can just delete the JPGs without a second glance!