I just got the new NTB for Firefox. Two things I noticed right away. First there is a white line between the NTB and Bookmarks Toolbar. It doesn't matter if I remove the Bookmarks Toolbar or add the Menu bar that line remains. Second the toolbar can be seen loading unlike the previous NTB for Firefox 40 and older.
Screenshot of #1;
It's now just like the Internet Explorer version except IE's loads better.