Re: No Balance No Aikido
One definition of Aikido that I have heard and really like is that it is applying all your focus and all your power at single point at a single time. Since this can best be done when you are completely balanced (or else some of your focus/power is elsewhere) then I would say that balance is key.
As Boon mentioned, in Yoshinkan this idea is practiced by paying strict attention to seiza, kamae, kihon dosa and kihon waza. Other styles have their own ways of working on being balanced and focused.
Eyrie's post also shows a way to accomplish this. As you go through his suggestions, pay close attention to your balance. As an additional point to his suggestions you might add a "do it carefully at 75% speed with a resisting uke. How's your balance then? What does that look like?" to the end.