Damn 1,000 word limit. Gotta make this quick.
The film is 2.5 hours long, yet feels like 5.2, and there are a few reasons for this. One of which is the fact that a preponderance of the first act is amateurish, conflict-free exposition, which does not bode well for repeat viewings.
The "learning about the dream world" scene is atrocious. No conflict. Both Leo and Page's characters already knew what was being explained. The similar "learning about the matrix" scene in The Matrix did it right by having one character not know anything. Plus, there was conflict. Neo gets his ass kicked and fails to make the building jump. Much more entertaining.
There's another problem with the whole section of bending the landscape where Leo explains the negative aspects of altering the dream world. The closest we get to seeing the dream world altered was Leo becoming Mr. Charlie, yet the most that happens then is a bunch of extras turn and look at Leo. That's it. The idea was not exploited. You literally have to go out of your way to miss that opportunity. Hell, that Mr. Charles scene is shorter than the scene that explains why altering the dream world is bad!
Let's not forget this whole idea of one corporation one-upping another has absolutely no personal ramifications for anyone on screen or in the audience. It would have greatly amped up the internal conflict if Leo had to struggle with the notion that helping the guy who could help him would endanger someone else close to him, or us, or someone else. ANYTHING could have worked better than an energy contract that means less to me than my neighbor's bath mat. Come on.
The totems were handled very poorly. All we need to know is their purpose. We don't need to know anything else, yet the film keeps piling on needless information.
If this is a heist film, where is the threat of being caught?
A van falls for an endless amount of time. Joseph Gordon-Levitt floats bodies down a hallway for half an hour, real-time. The guy from Bronson does his thing, whatever the hell that was. These are not complex tasks or events, but rather straight-forward in nature. Dragging them out for a solid chunk of the film is what creates the glacial pace and makes a long film seem even longer.
Inception has no real villain. You can make a case for Cotillard, but she is an internal enemy. She never takes a "physical" presence and never threatens anyone except Leo. Everyone else is dealing with faceless assassins. That makes it feel distant from the rest of the action. It doesn't even have anything to do, emotionally, with Leo's goal of getting home to see his kids. None of this is tied together. Leo didn't even know what the hell was going on with Cillian and never even knew of the outcome until after the fact. He's separated from the physical manifestation of his goal for a majority of the film. I ended up not caring if the plan succeeded. If it was all somehow tied together, the audience would be able to experience that great emotional catharsis that everyone was talking about...but that didn't happen.
In fact, Leo is so separated from the actual plot that you can literally put Levitt in his place and not even need the hero in the dream world at all! Hell, you can even put Page there, since all she does after designing the boring and lifeless dream worlds is hang out with the guys and tell Leo he's crazy. I really wish she had something else to do besides play the part of the fifth wheel.
Leo's lack of involvement in the main action of the story creates a 'so what?' moment when the problem is solved for him, and I can think of absolutely no reason why the hero should not be the one to conquer the main conflict. Brody kills the shark in Jaws. He doesn't send Hooper and Quint out to do his dirty work while he stays behind to deal with his fear of water. It's integrated. The hero is forced into dealing with the physical, and in turn, but learn to conquer his internal fears before he can conquer his external opponent. This is Screen writing 101, Lesson 1, and Nolan got that wrong. That's why I don't believe the reports that he spent 10 years writing the script since it only took me 148 minutes to figure out exactly what was wrong with it.
Not to mention the conceit that to enter someone else's dream and control it means that you would have to control your own subconscious, which they state elsewhere is impossible. Way to go, genius.
Pretty much everything this film does wrong, The Matrix does right. Watch that instead.
PS: The 'taking a scene from the middle and putting it at the beginning' gag reached its peak effectiveness in 2002 and has absolutely no place in modern films. It's getting as bad as that tired old 'It's all a dream' scenario. Oh, wait...