Firefox 13 has moved to the browser's beta channel today, bringing with it default support for SPDY, some elbow grease on default landing pages like the Home page, and better memory management for open tabs.
Having SPDY active by default means that, for sites that support it, they will appear in your browser faster than before. SPDY is also a more secure protocol than HTTP, which it's the successor to, because it uses SSL encryption for all sites.
The new Home page, available at about:home, puts many core Firefox features in an easily accessible location at the bottom of the page. These include Downloads, Bookmarks, History, Add-ons, Sync preferences, and Settings.
The New Tab page finally gets some interactivity to it, long after the other major browsers have adopted some variation of showing frequently visited sites. Also like the competition, you can pin sites to the New Tab page so they don't change, or remove ones you don't want showing up.
A change to how Firefox processes restoring tabs keeps them from automatically loading into the browser's memory when restoring an older browser session. This allows Firefox to be more responsive when starting, without removing your previous tabs from its memory.
Firefox 13 is scheduled to graduate from beta to the stable version of Firefox during the first week of June.
Correction, April 27 at 2:18 p.m. PT: Mozilla has changed its release notes to state that in-line auto-complete for URLs is not in this release, as originally reported. We have updated our story to reflect that.