So far I haven't had too much trouble with YouTube videos starting when I use Firefox 36, since you do have to click on the link to the video for it to start. It's just a matter of getting used to not having to click the "Activate Adobe Flash" icon before it starts playing. Then again, Firefox 35 is my default browser (I have both installed in separate program folders) and I also use the SeaMonkey browser (which is based on Firefox 35) quite a bit.