I dunno, Twes. I can put in my copy of Superman/Batman: Public Enemies on Blu-Ray and it'll remember where I left off months ago. Same thing for DVD's.
I can't figure out how to select commentary on some Blu-Rays, though. I guess I need to buy a remote instead of using a controller. I don't have a huge collection (Thank You, Netflix!) of Blu-Rays, so I haven't encountered the preview issues that you have. I actually still watch DVD's 80% of the time.