@DF: - Can user replace the battery or it remains to be the sealed type that can't be changed in the field? - personally, I would want to make sure that it can do USB host(without the dock); without this I don't think you can attach mouse/fold-away keyboard or any other interest stuff on the go? - in my book, portable h/d(I think that what is being used) is a bad idea.
USB 2.0 Host: Mass Storage Class (MSC) and Picture Transfer Protocol (PTP) (adapter micro B/A sold separately)