Simply put, Jetpack is a vehicle to bring some of the best WordPress.com features to your self-hosted WordPress blog, and it’s launching today with Gravatar Hovercards, WordPress.com Stats, the Twitter widget, a wealth of cool shortcodes, Shortlinks, LaTeX markup, Sharedaddy, and After the Deadline.
Of course, these features are just the launch set. There are plenty more on the way, and all you need to do is watch for them to magically appear in your Jetpack panel.
Have you tried Jetpack yet? What do you think of it so far?
Disclaimer: I work for Automattic, Inc.