Was good, could have been great. After watching this film several times now and having let enough time go by to really let the film sink in, I feel I can now write a well-rounded, as objective as possible review of the film. So here it goes...
Let me start by saying that I liked the film a great deal and it's "fun-factor" was quite good, but the film really missed the mark, in my opinion. While the film was good, it could have been spectacular.
Let's start with the acting. I can't say it was great and it wasn't ALL bad, but there was certainly nothing to write home about. Hayden Christiensen is nothing spectacular and comes off as rather laughable at times. Natalie Portman is normally quite good, was just OK in this film. As for Ewan McGreggor, I'll say this, his acting was well executed, but his dialog could have been much better. Samuel L. Jackson....well...he's a great actor and I love most of his films, but I sincerely believe that he should never have been cast for any of the SW films, he just doesn't fit with the character, nor can I take him seriously as a Jedi. I truly believe he just didn't work well with the role and the role would have been better suited for someone else. Ian McDirmid was just awful in this film. Normally he is a fine actor, even in the previous SW films and his other works. There were times where I thought he was fine, but there were many times were I couldn't help but cringe. I just wasn't impressed with his portrayal of Palpatine/The Emperor in this film. Everyone else in the film did a fine job.
Now for the story. I'm sorry, but it was just bad! It could have EASILY been MUCH, MUCH better. I didn't buy into the reasons why Anakin became Darth Vader and turned to the Dark Side, it felt WAY too forced. Not that it really matters, but this is what I would have done (and was hoping for): Anakin becomes increasingly impatient with the Jedi council and becomes more and more unpredictable (in the vain of him killing Count Dooku...I did like that), Padme becomes fearful of Anakin and decides it would be best for her (and her unborn child{ren}) to leave Anakin (with Obi-Wan's help). She proceeds to leave and of course Anakin wants to know where she is and what happened to her. Obi-Wan and the Jedis try to help Anakin understand that due to his actions she does not feel safe with him, etc... This, of course, only makes Anakin more angry. Then somehow amidst a fight or something Padme is severely injured and ultimately dies (unbeknownst to Anakin). Then Obi-Wan tries to tell Anakin that she has been killed and he does not believe him and is sure that he is simply trying to keep Anakin from Padme, so this begins his journey to the Dark Side, he begins to hate Jedi's for keeping him from his love. Who do you think would be there to help him find Padme? A certain Darth Sidious perhaps? Anakin then begins hunting down the Jedis, hell-bent on finding Padme, refusing to believe that she (and their child) has died...and when the Jedi's don't give him the answer he wants to hear...he kills them. This could also lead to a kick-ass fight between him and Yoda, where he really works Yoda, and thus forces Yoda to go into hiding until a match of Anakin/Vader's abilities can be found (this could take place after the fight between Obi-Wan and Anakin, so he's already become a cyborg, got the Vader outfit and had time to develop his Dark Side abilities). OK, so that's Episode III as done by LebowskiT1000. You may disagree with me that this would be a much better story, but it really doesn't matter, cause I seriously doubt Lucas is going to let me re-direct the film.
Let's talk about the directing and dialog. There are certain scenes, such as the scene where Mace Windu attempts to arrest Palpatine that were excruciatingly bad, everything in the scene was terrible, the directing, the dialog, the acting...just plain bad. Why did Palpatine's own electrical storm cause his face to get all wrinkled up? That was dumb! I always assumed that the reason he looked the way he did in ESB and ROTJ was because he was REALLY old (as he would be). Assume he's probably in his mid-to-late 60's in TPM, then he'd be at least in his late 90's to early 100's in ESB and even older in ROTJ, so of course he's going to look all wrinkled up and old. So, in my opinion you could have omitted the entire electrical-storm-wrinkling plot-point and it would have been a better film. There are many other scenes where the dialog/directing was less than stellar, but I'll leave it to you to find them an dissect them.
The bright and shining star in the film is the special effects. This is one thing that was really well done and if you disagree, then I'm sorry, but I'm going to have to disagree with you. The special effects are simply amazing in this film, all the CG worlds look great, the CG characters look fantastic and there really is nothing to complain about. General Grevious looks fantastic, by the way.
In the end, I thought the film was quite fun and worth my time, but it was VERY disappointing, it had the potential to be a fantastic bridge between AOTC and ANH and to just be an overall great film, but due to some bad choices in writing, directing and dialog, the mark was missed. Having said all that, I do strongly insist you watch the film yourself and come to your own conclusions, I hope you enjoy it. Thanks for reading my review/comment/rant.