I'm going to have to try this... so far I have only been shooting in the largest JPEG format with my 20D. I think it may be because I'm familiar with the JPEG format, i've been using it since my school days and I know how it works and how to best use it. But hey I guess its always good to learn something new... and yes it's true every time you save a JPEG it gets re compressed and loses a little more data... The only downside to RAW is the large file size, but then I have a 1GB card so it's less of a problem for me.