True Power of Windu?
Intrepid, somewhat direct movements are used in combination with very advanced techniques involving Force-powered jumps and motions. Form VII does not appear as fancy as Form IV, but the technical details of it use very open movements resulting in a very unpredictable battle style.
Form VII demands the emotional and physical intensity of Form V, but it much more effectively controls it (if mastered). Form VII, when fully mastered, results in extraordinary power.
However, as Mace Windu remarks in Episode III, Vaapad borders on the edge of falling to the Dark Side, as it channels one's anger and darkness into the attack. Only Windu's mastery and concentration of the Light prevents him from succumbing, which is why Vaapad is rarely practiced and very dangerous.
It is said that only two individuals ever outsparred Master Windu: Yoda and Dooku. (With dooku it would either be a stalemate or mace would win. When mace first sparred dooku, he was on the lightside, imagine how mace's vaapad would help him in a fight when dooku was on the darkside.)
Master Windu briefly fights General Grievous when the general and his forces overpower the Jedi and capture Chancellor Palpatine. Grievous is injured by Mace Windu using a Force grip attack on his chest, crushing the metal around his organs and causing Grievous to gain his coughs heard throughout Revenge of the Sith. ahhah! just thought that was funny.