I found some of the story a little forced, especially Anakin's abrupt change of heart in the scene where he pledges to Sidious. It's not that I think it was an impossible change, but I think it could have been handled a lot more convincingly, for example like this. I'm mildly fascinated with the light-side/dark-side distinction. It's presented in such a simplistic manner: light = altruistic, dark = selfish; light = equanimity, dark = attachment. Was it only me that thought that Anakin's desire to have a family was a reasonable one, even if it was forbidden by the Jedi order? Altruistic/selfish and freedom/attachment seem like false dichotomies. Maybe, to be fair to the movies, the Chosen One's role was to tear down *both* the Jedi *and* the Sith, to restore balance by getting rid of this dogmatic polarization. (I have to give credit to wynand for this idea.) However, certain details (for example, Palpatine's command for the army to turn on the Jedi was "order number 66") reinforced the impression of a rigid identification of dark-Force with Christian-evil and light-Force with Christian-good.
Anyway, I am interested to see the original three movies again in the new context of having seen the prequels. I was worried that they wouldn't work as well, but apparently Lucas had written out the plot outlines of all the movies before making episodes 4 through 6, so they might work all right after all. I did notice what seemed to me a "dumbing down" of the special effects at the very end of the movie (Vader's breastplate looked very primitive, for example, and then suddenly the consoles on the ship looked like something from 25 years ago too) -- presumably in an effort to taper off stylistically into the fourth movie.
Edit: Some other reviews/commentary that I enjoyed: