If there is any thought in the direction of being a 'password keeper' that should be a totally different extension and NOT interfere in any way, shape, form, look-a-like, et ceteras with the functionality of PassWordMaker in the form it is presently in.
Unfortunately, passwordmaker with autocomplete enabled interferes with firefox's built in password manager, there is no way to use them together, so if PM isn't going to re-implement this functionality there is no easy way of having it. Firefox encrypts your saved passwords on disk if you enter a master password, which gives a bit extra security against someone with physical access to your machine. PM doesn't currently do this for passwords saved with advanced auto-complete, and this hack mitigates that by at least requiring a master password before it enters a password on a web page. Personally I would like it if PM required the master password before doing anything
, and maybe skipped autocompletion for pages that found a match in FF's password manager.
So this means nobody can find this password in any way without the masterpassword. So even if somebody steals my laptop, I don't have to worry about my password.
If you look closely, it doesn't really add any security beyond requiring the master password to auto-complete. If you follow the original example, you can see that the letters of "secret" appear out of place in the character list, allowing an attacker to know the characters used if not their order. Even with a random-ish password saved in this way it would make brute-forcing trivial. A human-readable password becomes simply an anagram. You should still be very worried if your laptop was stolen!
As Eric says, the best solution is not to allow physical access to your machine.