Stuff I've gathered so far... 1 - The new tab page has been changed to a speed-dial (inb4 chrome fanboys; Opera did it first). 2 - Smooth scrolling has finally been implemented. It might take me a day or so to get used to it, but I like it so far. 3 - Tabs left alone for a while are unloaded or paged to disk? I'm not sure on this point, but if I go back and bring up a tab from a few hours ago into focus, it seems to have to load for a second (including the loading swirl on the tab's icon), 12 and below didn't do this. If it's unloading that could be annoying, if it's just paging that could be useful (as far as RAM usage and such). I mean of course there's more stuff... https://developer.mozilla.org/en/Firefox_13_for_developers But it's not stuff normal users concern themselves with. EDIT: Typos.