Xsheets are more effective for documenting the exact detail of movement and transition than they are at communicating the big idea. That's why they're often accompanied by storyboard panels or thumbnail sketches of camera movement.

As an interaction designer, I would consider using the xsheet approach if I needed an extremely accurate spec for an developer to code against. Maybe for geo-dispersed teams. But then there's the hurdle of educating a developer on how to read one.

My preference would be to storyboard timebased interactions. Storyboards with annotation can communicate both the big idea and the detail between. And if your developer is accessible and doesn't mind collaborating a little, you can refine the animation with them in real-time.

I'd like to see a breakdown of how the various columns in a typical exposure sheet are used.