Chrome user here since launch (who is also very entrenched into Chrome in terms of workflow): Ever since FF4b, I've been nearing a full switch back to Firefox, but the main deterring factor for me was performance. With FF5, the performance increase is absolutely noticeable and I commend the Mozilla team for their work. It's nearing a point where I'd like to switch back.

Now if only they can polish the Android browser a little more ;)