Rated 1 out of 5 stars

Tried on only 1 site, I only installed for that, and it's not working at all.
http://vindictus.nexoneu.com/

I only see the brown blackground for 3-4 seconds, and the page keeps trying 2-3 times in a second, even if the login options filled, but thats all, doesnt login.

This review is for a previous version of the add-on (0.3.9.1-signed). 

If the Firefox Password Manager did manage to save your password correctly and a special login bookmark is indeed created and used, should be able to auto-login. Perhaps the latest version 0.4.4 at https://addons.mozilla.org/firefox/addon/the-idle-login/versions will work.

As you have not used the add-on for other login sites and auto-login to them successfully, so can't really pinpoint the exact reason and find solution for it.