Most notably, JetPack’s new Slidebars (a play on sidebar) allow for quick access to both temporary and permanent information at the side of your browser window. Mozilla hopes they’ll be used for such things as watching a video while you continue to browse the web. Check out the demo video to the left for more details.
In addition, this release has added a couple of other mostly developer-oriented features called jetpack.future (that lets devs experiment with bleeding edge features) and persistent storage support for keeping settings between browsing sessions. For a more detailed explanation of the above three features, check out the post below.
Major JetPack Update: The “Future” Edition [Mozilla Labs]