Cavendish is the only program of its type, so there is no competition to compare it against. However, it is a very powerful program, and physically accurate (mind you, I won't be able to find a use for it unless I take astrophysics in college).

My only gripe with it is one of purism more than anything else- Henry Cavendish is presently turning over in his grave because you can change his gravitational constant. Boo. But at least you can now experiment with universes of variable mass.