Let's be honest... There's one thing that most people would love to experience with holography... I'll leave that to your imagination though.
On a technical side though, being able to collaborate over design or share a virtual whiteboard. On a gaming side, games like Minecraft seem obvious, but I'd like to see what it could do in other genres. On the hobby side it'd be cool to show me a 3rd person view while rock crawling so that I can more easily pick my lines and ensure my tires are where I want them to be. (Think switching to the 3rd person view versus cockpit view in any racing game.)