1) More screen space.
2) Smart keywords.
3) Keyboard shortcuts.
4) Auto-complete.
5) Tab navigation.
6) Mouse shortcuts.
7) Delete items from address bar history.
8) User chrome.
9) Create a user.js file.
10) about:config.
11) Add a keyword for a bookmark.
12) Speed up Firefox.
13) Limit RAM usage.
14) Reduce RAM usage further for when Firefox is minimized.
15) Move or remove the close tab button.