Rated 5 out of 5 stars

You got me wrong. You asked what extension did I have that modifies menubar. And my answer was that it's not actually an extension, that's a button (that contains the code I previously posted) for CustomButtons extension.
I know that disabled add-on are not active, and that's why I was almost stunned when I saw that your extension actually works only when I disable it and stops working when I enable it. That's hell of a strange.
>This AddOn does not move the menubar, nor it appends it as a child to the app-menu.
I was talking about my custom button, describing what it does - it actually moves menubar to the app-button container. But once again: now I've disabled that button, but your extension is still not working for me. And the code I've posted is not wrong, it's not a code from any part of your extension, it's a code of the button I had.

You just got me wrong.

And here is a new bug I just experienced with your extension enabled. The bug has gone only after I've disabled and _restarted_ the browser. Just disabling the add-on didn't help.
The bug was that "Error Console" just disappeared from the menu and CTRL+SHIFT+J did nothing.
And yes, I had devtools.errorconsole.enabled = true in the about:config. And I haven't changed that pref at all. Disabling your extension and then restarting brought Error Console back.
Please, take a look into that.

And don't be aggressive towards me, I try to help you to fix the bugs of your extension, as I like it's idea and would like to have it working.
Just take a look yourself: http://img59.imageshack.us/img59/3250/disabled.png - this is when your extension is disabled.
http://img59.imageshack.us/img59/1441/enabled.png - this is when it is enabled.

This review is for a previous version of the add-on (1.0.0.0).  This user has other reviews of this add-on.

I'm sorry we talked at cross purposes

Yes, I got you wrong. I didn't read it as answer to my answer, I read it as a new review. I'm sorry we talked at cross purposes and didn't want to sound agressive, so let's get the bug fixed:
I can't reproduce that New Old menu does work only when disabled, and I can't reproduce the error console thing. The following works for me:
1. Opening / Restarting Firefox with New Old Menu installed (-> New Old Menu changes are there)
2. Disabling New Old Menu (-> New Old Menu changes go away)
3. Pressing CTRL+SHIFT+J (-> Error console opens)
4. Enabling New Old Menu (-> New Old Menu changes appear again)
Did you try disabling other AddOns? The only AddOn causing problems I know currently is Personal Menu, but maybe you spotted another one?