So far, I have just been using my Bluray player as a regular DVD player with Bluray DVDs. That is, I have not bothered with any of the interactive features, etc. Aside from the obvious better picture, and better sound, these are some points I have noticed since I got my first DVD player (Oppo BD83) 3-4 weeks ago.
Able to skip FBI warnings, anti-piracy warnings, previews, etc. I used to get upset at “Operation prohibited” while trying to do these operations on a DVD.
It seems most Blurays, maybe all, do not support resume play from where stopped. I very rarely watch a movie from beginning to end. So, now with Bluray I have to skip chapters, and fast forward to find where I last stopped watching. It amazes me this feature is missing in Bluray.