I just saw it tonight (IMAX 3D), and I'm gonna state bullshit on much of the criticisms.
No, it's not a four-star movie... but is it worth seeing? Yes. (I don't understand what some critics thought was so bad that it made a "bad" movie rather than a movie that was enjoyable to watch. It's not a "no." Although maybe they just don't like superhero movies?)
And yes, the highlights of the movie are the actions sequences, plus pretty much anytime that Garfield, DeHaan, Stone, and/or Fields are interacting on the screen. The rapport is pretty incredible, that was worth seeing all on its own. They also do some of the Spiderman-swinging footage as if he's holding the camera, so you're almost seeing what he sees; and yes, U, you're probably more particular about your 3D than I am, based on what I've seen you comment on in the past, but I liked it.
I didn't find the characters difficult at all to follow. As far as three villains go, they're only ever on "one at a time" and there's no issues -- Electro is the primary villain, and Green Goblin doesn't come into until after that is resolved and you think you can relax (and you're tracking Osbourne's progress throughout the movie, so there is no surprise with it)... and the Rhino isn't really a character in the movie, he's like the Underminer who appears in the last 30 seconds of the Incredibles.... he was never meant to be a "real" character, he functions exactly the same as the Underminer did.
They also tied together the motivations of each of the main characters, especially the villains. It all syncs up, no one's doing something "just to be a creep" -- it's like watching dominos fall after the first half of the movie has been set up. The plot didn't have a LOT to it... but in that sense neither did Spiderman 2.
Finally, if you are all acquainted with the comic-book history, I'm not going to say how the movie plays out, but they do a pretty good job of going back and forth on it until the very end -- it had me guessing.
The Easter Egg clip in the credits, though, is pretty dumb. It's confusing to understand what is happening, and doesn't seem to be very significant at the moment.
I would have liked to have seen more of Chris Cooper. He's a tremendous actor, and I didn't think he got a lot to play with here.
And I agree with complaints about the Kafka guy -- what a stupid cliche, they could have done far better.
EDIT: Looks like I need to eat a little crow on the Kafka thing, since I didn't read the early runs of Spider-Man (i.e., 60's -> early 70's): I just saw this on Wiki regarding Harry Osbourne:
...Spider-Man pushes for Harry to get psychiatric treatment from Dr. Ashley Kafka, but he is ultimately transferred to the Vault.[6] However, the state is unable to put together a sufficient case against Harry, and after just a few weeks in prison he is released.[7]
The character might have been treated differently, but they swiped the name from the comic.