superb! Rated 5 out of 5 stars

Very helpful. Makes FF just as I want it to be. I even think it doesn't need this down arrow right to the logo.

This review is for a previous version of the add-on (1.1). 

Yes, you may hide the arrow via userChrome.css:
#appmenu-button > .button-box > dropmarker,
#appmenu-toolbar-button > dropmarker {
display: none;