See:-
http://dc.watch.impress.co.jp/docs/review/pview/20100315_353742.html
(in Japanese)
.. for an hands-on preview of a 645D beta unit for its appearance, size, weight and menus etc. Some size comparisons are also made against other Pentax bodies and lenses. Two mirror/shutter action video clips are also posted. There is no sample photo posted, though.