I just tested the latest nighly build (Firefox 4beta04), and found an interesting thing about organizing the tabs You can now group your tabs by themes, and show only the wanted theme. The other tabs are hidden on a background set manager (accessible from alt+space, or clicking on the tabset icon). The first time you open it, there's a video explaining how to use it. I find this idea very useful. I always have 3 firefox windows, each of them full of tabs. I can now use this option to sort by themes What might be great and is missing : - move sets from one window to another. - save / restore the sets (Session manager addon can be used in the meantime) Another update : they included Firefox Synch addon by default. It's used to synchronize your firefox profile over many computers across internet. It synchronize : bookmark, password, history, and opened tabs. Note for Ifish : The Persona bug is still not corrected. They are waiting for another bugfix before working on this one. They want to add the "Firefox" button on XP, classic, and aero first. After that, they will fix the "minimize/maximize/close" overlay problem from personas.