Runoff is important with soil, it's what allows salts to be washed away.
Babs34, I agree with you on soil dryness. It's funny how often people recommend one extreme to prevent another. Root rot is a very real concern for water sensitive plants, but bone dry soil is not an ideal solution.
For the fastest growth rate in soil keep the micro-organisms in the soil alive to maximize water and nutrient uptake efficiency. Let the soil dry out completely and all those micro-organisms die off and need to repopulate with the next watering.
Learn to read your plants, they'll tell you they're thirsty long before the soil dries out. For example: with Marijuana the leaves will point upward when the plant is thirsty, and they'll get stiff and curl downward when the plant is drowning. If the leaves are limp, or "drooping," then the plant is in shock and is approaching death.