Before starting the review, keep in mind that Firefox 3.6 will be the smallest upgrade Mozilla has released to date. Before this, version jumps have been in the 0.5 (Firefox 1.0 to 1.5, 3.0 to 3.5) or 1.0 (2.0 to 3.0) order, and while version numbers are not mathematically representative, the slight 0.1 version increase reflects the overall tone of this update, and Firefox development in general which is moving to a faster release pace.
Without a doubt, the most significant addition is support for lightweight themes, also known as personas, that was previously only available with the Personas extension.
A persona, which consists of a couple of images used as backgrounds for the toolbar and status bar areas, and setting a text color, is very simple to author, yet it significantly changes the appearance of Firefox and becomes a way of expression for the user.
To try it, simply visit Mozilla Add-ons, and go to the recently added Personas section. Personas are live previewed as you hover on the thumbnails, and become permanent when you click on Wear It.
Themes after all, personas are also managed via the Themes page in the Add-ons Manager.
Firefox has finally got tab preview, though it’s turned off by default. To activate it, you must set browser.ctrlTab.previews to true via about:config. After that, when you press Ctrl + Tab to switch tabs, you get a horizontal line of tab thumbnails.
You can also press Ctrl + Shift + Tab to get a preview of all currently loaded tabs, and even search the tabs’ titles which comes very handy when having more than 20 or so at a time.
A couple of special about: pages have been added. about:support, should become a troubled user’s best friend as it provides a helpful page with most details of your current Firefox settings including version number, customized preferences, and installed extensions; all of which can be easily copied to a support forum, email or chat window.
about: memory, is a first try on providing details about the current Firefox memory consumption.
Native videos now have a full screen option: right click on a video and select Full screen. On related news, a new full screen button is now available to add to the toolbars.
Tabs opened from a page (like when middle-clicking on a link) now open to the right of the current tab making it easier to reach content that we know is related to what we’re currently on.
A small but significant change: if you attempt to launch Firefox while only non content windows are open (like the Add-ons or Downloads Manager), Firefox won’t create a new window as before but restore the last closed window.
Autocomplete suggestions in previously filled web forms are now sorted by frecency, a combined indicator that tells how frequently and how recently an option was used. A nice addition useful in very particular cases though.
As announced before, Mozilla is now supporting the Web Open Font Format (WOFF) which has the advantages of smaller size thanks to compression, and the ability to trace the source of a specific font without the burden of DRM.
Finally, this beta introduces support for the new Windows 7′s taskbar previews feature. Don’t get too attached to it though, as it is buggy right now and may be pulled back depending on how it evolves in the next few days.
Further Windows 7 integration like showing a download progress bar in the taskbar and jump lists are also in the works but unlikely to be ready for Firefox 3.6.
The current nightlies are labeled pre 3.6 beta 2 suggesting a second beta may be the next step. This would be in line with the latest roadmap.
Not much is left for future development releases. One final feature could be per tab network prioritization which will make Firefox allocate more bandwidth for the currently viewed tab, less for other tabs in the current window and even less for other windows, enhancing the perceived responsiveness.
As usual, a critical subject are add-ons. Right now about half of them have been updated to some 3.6 development release. You can help increase this number by installing the Add-on Compatibility Reporter. Once installed, all your extensions will be enabled. You can then check and see if they work or not, then go to the Add-ons Manager and report whether it works or not.