Wow this is fantastic. I really wish Apple would give us this kind of insight into iOS.
It was always possible to see an install referrer if you set up the right listener in your AndroidManifest.
It seems that the link between the market and analytics will now give you more funnel like stats, as it includes views of the app details page in the market itself. (It's interesting to see what this will do to competitors of analytics, it seems it's not possible to get this information in any other way than connecting with Google's product).
effing finally.
Up until today, there was LITERALLY NO INFORMATION from Google about where your installs came from.