So far I've noticed Resume Play disabled only on the Disney (or Disney distributed) titles. Generally true for previews as well. I figure the Resume Play issues is simply a mastering issues that someone is unaware of because there is no logic to it and it only seems to happen on their disks. The preview thing I'm sure is intentional.

Strangely my Blu-Ray player remembers the stop location of a DVD even when powered off, but will not remember the stop location of a Resume Play enabled Blu-Ray when powered off.

Give them some time and these things will go away just like they did with DVD. I had a first gen DVD player and lived with it's ideosyncracies until last year when I got the Blu-Ray player which is a much better DVD player,but leaves a little to be desired as a Blu-Ray player.