Well, it certainly crashes on all my Windows flavors (XP, 7, 8x64). Firefox isn't exactly the poster child for stability, can't tell whether it ever was...

Any browser that can be locked up by a bit of JavaScript that hogs the thread really needs to have NoScript enabled. The reason is there are too many easy ways to write a processor hog, either intentionally --

    function hog_processor() {
      while(true) {
      }
    } 

-- or unintentionally, by not knowing something about programming:

    function beginner_error_run_forever() {
      for(var x = 0;x != 10;x += .1) {
        // code here
      }
    }

You're right, but Today's World really relies on JavaScript and browsers development could, well, weigh it a bit more. Fighting on speed records might look good on browser's CV but for me personally doesn't matter zit - I'd take a stabler Firefox over a speedier one any second (I say this after 2 crashes today, on 2 different machines).