Yeah I want to know when are they going to make the design a little more compact sans the unnecessary statusbar in Firefox. Just provide more real estate and also try to make installing extensions as painless as possible just like Chrome.
I don't think Mozilla is capable of making Firefox as fast as Chrome (for at least few years or so) so let's just leave on that.
Sorry for the really late reply, but the Mozilla Jetpack project is their lightweight extension system. It's still in development, but there's enough going on to be pretty useful already. https://mozillalabs.com/jetpack/
Also, from the View menu, you can disable various toolbars and the statusbar. Right-click a toolbar and click Customize to use smaller icons or even text-only labels.
I don't think Mozilla is capable of making Firefox as fast as Chrome (for at least few years or so) so let's just leave on that.