For me, most the bad things weren't as bad the second and third time around. Like Vader's "NOOOOOO!" The first time I heard it, I was horrified. The second time, it still sounded dumb, but I didn't really take as much notice to it. And the third time, it hardly ruined the scene at all, thought it would still probably be better without it.

General Grievous also got less dumb the more times I watched it. It might just be the fact that I knew it was coming, so i was able to prepare for it. The first time, all the dumb stuff caught me completely off guard (even though I was expecting it to be dumb, I didn't know where or when the dumbs parts would be).

Padme's death at the end got dumber the more times I wacthed though. The first time, I didn't even care about the "She's lost the will to live" line, but now I think it's a horrible line. Same with Palpatine telling Anakin he killed Padme.