These were on the Gadget show a few weeks ago, the Sony came out on top out of the few they reviewed.
I had thought of doing the same thing but got the impression from the reviews that they used their own file format and therefore you were limited to purchasing files from their own sites, i.e. you could not scan your own books / IR plates / etc in and use them.
What file format do the files take and is it easy to make your own? (As some appear to have been doing successfully)
J.