Great work, it's the first Open Graph plugin I've used that actually does what it says.
The only thing it seems to be missing is og:type. I get this error when I use Facebook's debugger:
og:type is missing. The og:type meta tag is necessary for Facebook to render a News Feed story that generates a high click-through rate.
Is there any way to include that? I'm guessing it's just one line of code in the output php file, but I've no idea what that would be...