A quick click on the button and, instead of looking at the Earth, I'm looking at the sky, with all the obvious constellations and asterisms marked.
The sky is littered with various dots of different colours (red for Messier, Blue for NGC, blueish swirl things for Hubblesite), when you click on them you get the usual Google Earth pop-up bubble thing with information about an object at that location.
As you'd also expect: pick a DSO, zoom in, and Google Earth downloads nice pretty pictures for that item.
Well, that's it for the first 5min play. It's pretty much what I expected it to be. I can't imagine that I'll be dropping my use of Starry Night for this any time soon, but I can imagine that this will be useful for other purposes. The first thing I want to look at is what's required for a KML file that can be used in Sky mode — I can imagine using this for a few things (and I bet Stuart will be looking into that pretty soon too).