I switched to Firefox from Chrome a couple of months ago, and liked it so far. The UI is fine, and the speed is also fine. But the MacOS+Firefox+Gmail bug (https://bugzilla.mozilla.org/show_bug.cgi?id=341886) drives me nuts. Can't jump to the start or the end of line while editing the message (OK, it is possible with emacs shortcuts instead of standard Mac shortcuts). Can't select text from the current position to start/end of line with keyboard (emacs shortcuts don't help). I haven't appreciated how much I used these shortcuts for email editing before switching to Firefox. And the bug is open since 2006.