How cool is this? Carter Maslan points to the Virtual Earth Interactive SDK:

"The SDK is organized by the things you want to do, and each of those things is correlated to a live running sample, source code, and reference documentation - all one tab click away."

You might provide the most wonderful APIs to the coolest app ever, but if it is hard to use or hard understand it won't be used. I think the Virtual Earth team have done a really great job of providing usable developer experience. API usability in action:

In this case, want to Use a callback to this point on the map:

I then click on the 'Source Code' tab and it shows me this code that I can copy and paste:

And / or click on the 'Reference' tab to show me documentation related to that function:

So simple, so sweet.

Have a play.