Here are a couple of applications that can improve the Unity experience. Superswitcher which is an awesome alt+tab alternative, Unity 2D for performance (no compiz) and gnome-do because It has features unavailable on unity app launcher.

My favorite superswitcher features is that I can change to an opened window by typing its name. Switching windows this way is very fast and has improved my work flow greatly. http://code.google.com/p/superswitcher/ I have superswitcher set to capslock key since I don't usually use capslock.

I also use and like unity super+NUMBER key launchers.