I guess the only recommendations that would have value would be from people with the same display otherwise there views are coloured by their viewing hardware
As a general guide stay away from animation/cgi which tends to look good on anything.
Legal material would mean sticking with the demos as listed or the HD DVD's that contain a WMV version of a movie at 1280*720p.
So far I have not been greatly impressed with the quality of those (only watched two though) but the source material may have more to do with that than the actual encoding and mastering of the disk.