We’ve been playing with it. As developers we’ve checked our themes, plugins and widgets. We’ve talked about it in the WP develoepr community. We’ve seen things we really liked and saluted. We’ve seen things we didn’t like and submitted them for changes … and finally, after months of hard effort – WordPress 3.1 is live!
If you host on the free WordPress.com site it means you’ll see a few new features like I wrote about at WordPress 3.1 – Developers get ready. That’s really about it.