Edit on February 14, 2017: I modified the code to handle autocomplete being set in input fields as well.
I don't know about you, but when I see a form that has disabled autocomplete, I get pretty upset:
I understand the logic behind doing so on certain secure forms, but when I ran into this a few minutes ago for a freaking survey I wanted to punch my screen. (Ok, maybe I need to take a deep breath and relax too. ;)
I'm sure this could be written better (maybe instead of always removing the attribute it could always enable it), but on my limited testing (the form that ticked me off) it worked perfectly.