Truly amazing (no pun intended), this film vaults over the first movie. Better story, better villain, better characterization, better effects. Those who know next to nothing about Spidey other than what they saw in the first movie (like my wife) will love it. For those who have been Spidey fans for life (like me!), it is as close to geek perfection as we'll ever see.
Compared to many other superhero or blockbuster action flicks, the big action scenes are actually few -- but they all come as a direct result of the story and after you've gotten to know the characters involved, which makes the stakes that much higher. I know it should be common sense to say, "Focus on the characters!" but look at how often it's gone wrong in the past. (Pick any of the Batman films, especially the last two, for examples of movies that forget there's more to a good story than rubber nipples.
The movie works for three big reasons: 1) You feel for Peter Parker, and you really want him to win; 2) It's truly a Sam Raimi film, with wild "tentacle-cam" shots and lots of screaming people; and 3) Alfred Molina kicks ass as Dr. Octopus.
Years ago, when James Cameron was trying to do a Spidey film, I was hoping he'd get Ah-nuld to play Doc Ock, but I know now that would have been terrible. He would have hammed it up, whereas Molina plays it cool and dry, letting the tentacles do most of the action.
Go see it!