Rated 5 out of 5 stars

OMFG, I thought your extension adds Character Encoding to the top-level menu and that's why I've installed it. Nvm then, your extension works for me. I just expected something else (should have re-read the description more carefully).
EDIT: thanks for that small extension for me - now I'm happy.
> // Remove Charset Button (avaiable through View Menu)
> remove(document.getElementById("appmenu_charsetMenu"));
And why do you _delete_ items in your extension? That is the cause of all the errors.
You'd better add id or class to those elements and hide them using CSS style: .someclass {display:none;}

This review is for a previous version of the add-on (1.0.0.0).  This user has 6 previous reviews of this add-on.

New Old Menu removes Character Encoding menu item in top level menu (is in view menu on the right side). After disabling New Old Menu, I see it - but it seems to be hidden sometimes by default. Why do you ask for that?
EDIT: Character Encoding is there by default, but I don't know what reasons it appears - or not. I created a little AddOn for you to disable hiding which you can download at http://dl.dropbox.com/u/26332445/alwayscharset_1.0.0.0.xpi , but I won't upload it here, because I think there was a reason for it to hide per default.
EDIT2: I didn't think of that option while coding this. But I implemented it now; 1.0.0.1 is not reviewed yet, so you can only download it via the version history.
EDIT3: 1.0.0.1 is reviewed now and should get installed via automatic updates.