I should have said more about the profiler in case you're new to it. Let it run. It's overhead is really quite low. Then when you notice the slow tab switching or janky scrolling, you hit Capture Profile and that stops the profiler and loads the profile for you to view. IN that view you'll find a "share" button in the top right that makes the profile remotely available and gives you a link you can use to file a bug at https://bugzilla.mozilla.org
I will. I was actually intending to put Firefox aside for a beta release or two, but I've enjoyed using it so much aside from those issues that I think I shall persist for a while.
