It's useless till it comes to blu-ray, then it'll be fantastic!
I don't get it, eventually interactivity will be matched such that the only difference between the formats will be the size and data rate. Just because a feature isn't used by someone, doesn't mean another person doesn't find value in it.
I doubt I'd waste my time on it, tell you what, I wouldn't mind a feature that allowed me to find out what a piece of music playing during a scene was etc. hmm... I could see a few uses for such technology.