It's definitely the best of the prequels, which isn't saying a lot, but it's also quite the diamond in the rough. I really missed that there was no 'birth' of the rebellion, a handful of senators from various systems meeting in seclusion to start organizing against Palpatine's power grab. Some of the obvious allusions to current American politics were unnecessary and heavy-handed. A lot of the duel choreography was either poorly captured on film (for example, where exactly did Sidious strike down the three masters who accompanied Windu) or had so much background noise in terms of color or motion or clutter (Lucas' visuals are like an interior decorator on crack-cocaine) that you couldn't enjoy the foreground action as well as you would've otherwise; sometimes, less is more.
Also, the geek in me wants action that rigidly allows you to deconstruct who the most powerful force user really is, a sort of pecking order among the major players, and the fight scenes were just too unsatisfying for that. I'm already seeing wild conspiracies about how Sidious simply held back on Windu, ignoring the fact that he couldn't have been 100% certain that Anakin would arrive or arrive in time, and that before Anakin entered the office Palpatine was disarmed and kicked to the floor (not a tenable strategy for that point in time, particularly after years of deft political and personal manipulations on Sidious' part). And why the Yoda-Sidious fight ended the way it did left me scratching my head; with the stakes so high for billions of people across the galaxy, a supposedly selfless jedi would've given more, risked personal life and limb, to end the coming tyranny. Yoda = pussy.
Visually gorgeous film, though as usual Lucas has no idea how to marry those visuals with a narrative that elicits an emotional buy-in from the viewers that would heighten the impact of the onscreen action. The end of the Obi-Anakin fight was an annoyingly obvious plot ploy ("it's over, I have the high ground now!" Umm, what_the_f*ck is that supposed to mean for people who can leap dozens of feet up into the air) and very unsatisfying on several levels. Meh. And Vader's temper tantrum was a wee-bit too much of a James Whale rip-off.
Best scene of the film: Yoda fighting outside the jedi temple and jumping up onto a trooper's chest and spiking him with his saber.