I have Epson P-4000 which is great, but after i upgraded to 1DsIII and Hasselblad i was worry that P-4000 80GB will be not enough, so i went with Vosonic VP8860 500GB, as a space it is incredible, but as functions or performances or features i really miss Epson.
I have an Epson P-5000 for use with my 40D and G9. It's great for off-loading my CF and SD cards at the end of the day when I travel. Best part is that you can do some editing and get rid of shots that just didn't turn out, and pass the thing around to share your photos.
Surprisingly, all the Epson viewers currently do not support RAW format for the 5DmkII. They put out a firmware update earlier this month (July 2) which added several additional RAW file support for Canon cameras (XSi, XS), but so far, no RAW support for the 5DmkII.