The words "Sony" and "open" do not go together in the same sentence - look what they did with MP3 devices - completely proprietary technology requiring you to re-rip your CDs or convert your MP3s to their closed format.
Expect the same here, would be my guess - but someone with a bit more consideration for end-user requirements is bound to use the Philips display in their own device in the not too distant future.
As with most things of this nature, cost is likely to be high initially - I would guess around the same price as a high-end PocketPC. BUT, to catch on, this technology needs to be available to the masses, since it is a single-function device (well, I guess they could build standard PDA functionality in there, but that is not really the point of this device). Prices would drop fairly quickly.