Booted to Ubuntu, it wants to install new Firefox. Okay. Here are the first impressions: TL;DR: It's terrible. The designer hipsters are now ruining Firefox, too.
1. Why are the tabs again above the URL bar? I have configured them time after time below. But this time, the option to put them back below is gone even from about:config! WTF?
2. Where has the "add-on bar" gone? Wasn't it enough that the status bar was replaced with the buggy text that shows on mouse hover?
3. Google "firefox 29 tabs below url bar", people are recommending this add-on. Thought: has Firefox really gone the way of Windows 8 where you need to install 3rd party extension (Classic Shell) to band-aid the catastrophic damage the hipster designers have done to the original product?
4. Reboot the browser after installing the extension. Spend 20+ minutes making everything as close as possible to what is what before.
5. Finally, continue working. About 2 hours in, suddenly my back/forward buttons stop working. Assume the extension is interfering with core somehow. Fortunately, rebooting the browser helps. Some time later, this happens again, need to again reboot Firefox.
6. Seriously consider switching to Google Chrome. The few reasons to use Firefox are evaporating fast.
Overall experience: 30min spent fiddling with Firefox settings. There is currently no easy way to make it like it was before. If you are running Firefox 28, I would suggest waiting a few weeks before upgrading until there is an easy and tried way to un-fuck the UI.