The one-click install of Personas is good but I am not really that excited about the feature. Protection from out-of-date plugins looks interesting. A feature that I missed noticing for sometime is that the new tabs are now opened next to the tabs that open them and not at the far end as before. Again, my bad missing the beta version. However, there is a config option to make the tabs open at the far end. Changing the option “tabs.insertRelatedAfterCurrent” in about:config to false is all it takes. Got this trick from here, where I also found out how to do prettier tab switching. Of course, the config option “browser.ctrlTab.previews” is set to false by default.
Side note: Firebug 1.5, ready for Firefox 3.6, was released just a day before the browser!