I also still use Firefox on my faster computers. The "freeze" isn't as severe as it is on my older, slower computers. Like I mentioned, CPU speed has a lot to do with how long the "freeze" lasts. But, like you, I use Firefox for all of the add-ons that it has available (and that I use). Many of those add-ons don't have replacements on Chromium. And definitely not on Opera, which seems to be the weird duck of the browser bunch. Opera is a nice browser ... don't get me wrong ... but it does so many things differently and no one seems to want to write add-ons for it.
As for Windows, I cannot weigh in. I don't run Windows unless I'm forced to (like at work, and even then I grumble about being forced to use the most insecure OS on the planet to record mission-critical, life saving information on).