I think a lot of my issues with Firefox stemmed from my PC, which was very cheap, 4 years ago (read: not a lot of free resources, though it handles Chrome alright, which is a known resource-muncher). 
Each new update that FF had, it would just get worse. The big tab spinner* would stall pages for up to several minutes at a time, occasionally crashing the browser, which was a real time killer as the main browser I use needs to able to switch between several tabs and have the pages be responsive, and with FF it became faster to close the browser and restart it if a tab was idle for longer than around 5-10 minutes. I tried every suggested fix, but nothing helped, and then the update they released, which caused me to download Opera, was one that resulted in FF always crashing every time I went to download something.
*Which also happens to a degree with all browsers I've used, but Chrome reloads pages rather than basically kills them then attempts to recall them, and Opera is a lot faster at recalling and becoming responsive than FF ever was.
