"...my 20d to shoot raw & jpeg simutaniously..."

My friend with the 20D does that and what she finds is that the jpegs look distinctly "softer" than the RAW files - maybe it's using a higher compression than normal, but they are unuseable for finishing. When she shoots in just jpeg mode they look better - she can actually use them for finishing.

She says she uses it to preview the images - but she's scrolling through both the RAW and the jpeg (2 of the same image) so it does her no good the way she's using it.

Basically, it's so you can quickly burn a CD of the jpegs for the client without having to wait for any software to batch-convert them. that way the client can preview them for composition, to make sure everyone is smiling and in place, and it's the same numbe as the RAW file so they can tell the photographer "I want you to finish image numbers..."

She can actually get away with shooting in jpeg for her professional work because the magazine she shoots for is only 5x7 inches.