None of the new features in Firefox 5.0 (or 4.0 for that matter) show up in the Firefox menu bars and window. I get the same behavior when upgrading on three different PCs with two different operating systems, so it doesn't seem OS dependent.
Getting this behavior running on a Dell desktop running Windows 2000, a Dell laptop running XP and a no name desktop running XP. None of the new buttons shown on the new features page http://www.mozilla.com/en-US/firefox/5.0/whatsnew/ show up on any of my browsers.
Krejt Përgjigjet (1)
Some of the new things are not shown by default in XP but easily established.
Right click on a toolbar space and
* Uncheck the Menu Bar; this will hide the Menu Bar and show the orange Firefox Button in the top left hand corner. You can toggle from one to the other.
* Check Tabs on Top. This will move the Tab Bar above the Navigation Bar - remember you are not showing the Menu Bar. I must admit that I prefer tabs in their traditional place where they are nearer the web page action.
For moved and combined buttons this will help -
http://www.mozilla.com/en-US/firefox/features/
I hope this is what you are after.