This thread could really be going places.
I say good aikidokas are powerful.
In order to be powerful they need to be strong.
On the other hand I have a friend who is strong but not powerful in the grappling/moving sense, wierd.
So I reckon good aikido needs both simple physical strength and aikido-type-power.
Don't get too fluffy-bunny or you have no chance to be martially effective.