I was in the same boat a couple of weeks ago.
I looked at most of the major vendors out there, Epson, Wolverine, Hyperdrive, etc.
Based on the research I did Hyperdrive is very very fast in xfer speed.
I also emailed both Wolverine and Hyperdrive to confirm that they do not support Epson raw file. The only unit that support native Epson raw viewing is Epson's own.
However if you shoot Raw+Jpeg then you will still be able to view them on any of the non-Epson units. Given Epson's high price, big size and weight, I think it's better to get a Hyperdrive unit and use the extra $$ money saved to get additional SDcards, if the extra 3MB of Jpeg file causes storage problems for you.
The only other advantage I see for the Epson unit (the newest one) is that you can attach an external harddisk to it and make backup copies out of the Epson unit. But then again for that price, I can get a color screened Hyperdrive and any other cheapo brand units as the backup unit.
John