I've noticed that if I restart FF, JS is always re-enabled, even if it was switched off previously.
Because restarting re-loads all previously open windows and tabs, this means that they always re-load with JS enabled, which is very annoying: Often unwanted videos start playing, etc. In some cases (if you've turned off JS to block potentially malicious scripts), it might also be a security risk.
I'd like to suggest that the extension should remember its previous state after a browser restart, to fix this problem.