The "awesomebar" (that's the nickname for it...) sucks, get the
oldbar extension to restore the addressbar from FF1/FF2.
If I'm reading this correctly, after user protest Mozilla decided to hide the home button only
when your Bookmarks are open on the left side for Firefox 3 Beta 4. If you don't have bookmarks open, from FF3b4 on it should display the home button as it was.