Not sure if this is the right place (?)
Had to revert from the latest Nightly that was released today (Sep.17) to:
firefox-35.0a1.en-US.win64-x86_64.zip 15-Sep-2014 11:11 49M
* Session Manager icons disappeared from the address-bar, and would no longer function. Tab Mix Plus' session manager tried to take over but it couldn't read SM's files it seems, as sessions were listed as empty.
* Tabs wouldn't seem to load (at all/sporadically).
* Tree Style Tab broke completely. Changing settings for position Top/Bottom/Left/Right, would do nothing.
* User Styles worked sporadically - would colour backgrounds of tabs, but not the text - so could not see tab titles (black on black).
There were probably more issues, but those were the things that jumped out immediately.
* Opening Addon's from the MainMenu-Icon wouldn't show the Addon's page, it was blank. Though switching tabs and switching windows sometimes got it to display.
(Posted from IE - don't shoot me :: while FF installed, launched, and loaded tabs).
Back on 15th September's release; Everything appears "normal" -- for nightly that is