These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Complete Monster: Palpatine. Add-on materials including the novelization reveal he was angry at Anakin for losing to Obi-Wan and considered leaving him for dead since he was crippled both physically and in his strength with the Force. The only thing that convinced him otherwise was that Anakin would still be powerful even in this state (that said, in the movie he seems only to be impressed that he was alive, and isn't angry at all).
Contested Prequel: Like the other two prequels, though leaning more towards the positive end of the spectrum.
Critical Dissonance: Gets enough flak from fans that its Rotten Tomatoes rating of 80% might surprise some people.
Fight Scene Failure: The Palpatine/Windu fight looks rather pathetic, due largely to Lucas' insistence that the elderly Ian McDiarmid do it himself instead of using a stunt double and digital face like they did for the Dooku/Yoda fight in Attack Of The Clones.
He Really Can Act: For a few minutes when he has no lines as he begins the massacre of the Jedi Temple, Hayden Christensen is genuinely scary looking as a dark-sided Anakin, now Darth Vader. Of course, when he has dialogue again, he's a whiny brat again.
Was done to Mace Windu and Aayla Secura, even though they're both killed onscreen.
Mace's survival is at least somewhat plausible. He loses his hand, gets zapped by lightning, and tossed from a significant height, all of which Jedi are shown to be able to survive throughout the saga (although never all at once.) Secura however, gets shot in the back by at least a dozen troops at near point-blank range, and her body continues to be shot as the camera pans out.
Hype Backlash: This movie is often lumped together with the other two prequels and declared to be just as bad.
Idiot Plot: Much of the reason Anakin loses trust in the Jedi and eventually betrays them is due to them not trusting him, thus giving him good reason to do the same. In the end, Anakin's betrayal of the Jedi was as much them pushing him away as him turning his back on them.
Magnificent Bastard: Palpatine. He plays every single character in the movie like a fiddle and becomes dictator of the galaxy by the end of the second act, and by the end of the movie all of his potential enemies are either dead, on the run or on his side. Granted, at least part of this is because some of those enemies are not always the brightest folk, but they suspected that something was wrong with him being in power so long and thought at the very least that the Sith might be controlling him, and he still covers his tracks until its too late for them.
Memetic Mutation: Vader's "NOOOOOOOOOOOOOOOO!!!" has since been used as a way (mostly in jest) to show great disapproval over things on forums and message boards.
The NO part also spawned a different famous meme thanks to a cheap chinese bootleg of the movie having horribly translated subtitles in english. During the scene the "no" was translated as "Do not want!" which quickly became a reaction comment towards unwanted things or gross images.
"You underestimate my power!!!"
"Only a Sith deals in absolutes."
"You were the chosen one!", usually in rage comics to show betrayal but full variations of the quotation have been made◊.
Rooting for the Empire: The actual reaction of the Senate when Palpatine declares The Republic shall now become The Empire, is one of thunderous applause. And in all honestly, given how utterly incompetent the Republic was, despite being evil, is the Empire's ability to actually get things done, necessarily a bad thing?
Yoda may have been feigning his surprise to confuse Sidious. Notice he recovers fairly quickly. On the other hand, Mace Windu was downright stupid: he had a Sith Lord right in front of him, unarmed but still clearly dangerous, and he doesn't even think to incapacitate him or, you know, chop off his hands so he couldn't use it.
More likely Yoda just underestimated Palpatine. He has casually deflected Force Lightning before (from Dooku in the previous film); he thought he could do so again. Palpatine was stronger than he thought
That scene was kind of narmy because of how easily Palpatine and Yoda blasted each other with lightning / telekinesis while the recipient just sat there and took it.
In the junior novelization, Yoda deliberately took the blast to trap Sidious. Not that said trap really did much.
Anakin for believing absolutely everythingPalpatine tells him, especially his claim to be able of saving Padme after revealing his identity as Darth Sidious (the ultimate source of all the previous attempts on Padme's life).
Averted, for a minute or two, when, upon having Palpatine more or less tell him outright that he is a Sith lord, Anakin DOES immediately tell the Jedi council, who immediately attempt to arrest him.
Padme. Anakin just told her that all the Jedi turned traitor and are being destroyed, Obi-Wan tells her that the younglings all died, she sees the Jedi Temple going up in flames, and she STILL doesn't believe Obi-Wan.
Denial while in shock about someone you love being accused of something horrific is hardly idiocy. Besides, how could she know Anakin burned the Temple?
Papatine, seriously? Why keep casting force lightning while it's rebounding back and disfiguring you?
Fridge Brilliance: He uses his disfigured appearance to further slander the Jedi to Senate: "The attempt on my life has left me scarred and deformed."
And he was trying to make himself seem defeated while simultaneously holding Mace Windu off. If there had been no lightning, Windu would have killed him before Anakin tipped far enough.
Mace Windu bringing down his lightsaber so slowly when trying to kill Palpatine. Seriously - it looks like Samuel Jackson is trying to replicate the effect of slow motion without actually using slow motion. Just friggin' cut the bastard already, Windu!