1. Within a modeling system executing on a computer system, a method of visualizing a circuit design comprising: identifying the circuit design; reading hardware cost information for the circuit design; presenting, using the computer system, a graphical representation of the circuit design having at least one visual characteristic on a display coupled to the computer system; varying the at least one visual characteristic for a circuit block of the graphic representation according to a measure of hardware cost determined from a cost function that depends upon at least one item of the hardware cost information for the circuit block, wherein variance in the at least one visual characteristic indicates the measure of hardware cost; and concurrently with varying the at least one visual characteristic of the circuit block, representing a reduction in the measure of hardware cost using a second visual characteristic of the circuit block, wherein the reduction in the measure of hardware cost is shown using the second visual characteristic only when the reduction in the measure of hardware cost exceeds a predetermined amount.