I agree 100% -- and I forgot to mention that Twyla Tharp's choreography is awesome.I agree - I find the performances spot on. John Savage is weird at the best of times, but his work here is terrific.
As I have mentioned, I've never seen the original stage production, but to me this films works thanks to a lot of it being shot on the streets and using dynamic camera movement. In that regard it is no doubt a huge departure from how the original production was deployed. The editing also heightens the dynamism, and makes this a great cinematic musical in my humble opinion.