Rated 5 out of 5 stars

It seems to be intentionally making the addons bar visible and moving itself back there after I move the button to the tabs bar and untick the addons bar :(
Would the code at http://mike.kaply.com/2011/01/25/the-firefox-4-add-on-bar-for-developers/ prevent that?
This is a great addon to point people to that keep pestering us on IRC about "when will Firefox 4 come out?"

This review is for a previous version of the add-on (0.8). 

Yup, this extension exposed multiple bugs, and two of them are matching what you described:

https://bugzilla.mozilla.org/show_bug.cgi?id=627484
https://bugzilla.mozilla.org/show_bug.cgi?id=627886

Would love to see them patched :)

Rated 5 out of 5 stars

Great Add-on, the only problem that I have experienced is that the extension toolbar button distorts the height of both Navigation and Bookmarks Toolbar if placed there. My solution is placing it on the Menu bar or leaving it on the Add-on Bar.

This review is for a previous version of the add-on (0.8). 

It's fixed in version 1.0.1, please update to it :)