Although I really like the lightsaber fight between Palpy and Mace - the idea that his unorthodox fighting style is something the jedi were not prepared for.
I would also have preferred smoother deterioration. Maybe each active use of the Dark Side could be explained to increase the rate of deterioration.
I wonder if it would be worthwhile to alter his skin color to be less saturated before the duel and more blurry (to smoothen wrinkles) afterwards. I am not familiar with after effects tools at all, and am afraid that it might be too much manual work for too little effect.
When I look through the trailers I get the feeling that Palpatine's charge is longer there than in the movie... Perhaps those frames could replace the spinning. I'll have to rip and check frame by frame to be sure.