Superheroes and superhero movies are only as good as the villains with which they must battle. Near the beginning of the film we are introduced to Flint Marko (played by a bored looking Thomas Haden Church) who will become the Sandman. His character development consists of his love for his daughter, and well that is about it. Through contrasting shadows on his face, Raimi uses a cliched symbolism technique of showing that while there is a dark side to Sandman, really he is just a good guy.
Sandman's origin story consists of him running from the cops and falling into a some kind of experiment involving, you guessed it, sand. Somehow the "scientists" don't realize a human has entered their experiment and turn it on. Then the sand somehow forges with Marko, and he is now made of, yup, sand. Somehow he can wield this sand to become a huge, as tall as a building, sand monster capable of smashing anything in site, or he can look just like his former self.
Conveniently, Spiderman 1 is rewritten to have Marko responsible for Uncle Ben Parkers death giving Peter, and the audience a desperately tacked on reason to even care about his fate. The effects when he transforms into the giant Sandman are poor and Thomas Haden Church's stone faced portrayal make in look like he'd rather be in some independent film sipping wine.
To try and defeat Spiderman, Sandman teams up with Venom who doesn't even make a full appearance until about 30 minutes left in the film. His origin is even harder to explain. Early on Peter and Mary Jane are too busy being gaga over each other to notice some kind of black symbiotic substance fall at terminal velocity out of the sky and jump on to Peters scooter. For some unexplained reason or origin this substance chooses Spidermans suit to bond with, thus turning the entire suit black and giving Peter almost euphoric sensations and power that he cannot control. The suit turns Peter into an over-confident, over-bearing and complete asshole. The power corrupts him so much that he eventually decides to rip the symbiont off which can only be done with the toll of a bell, or something. His arch nemesis photographer at the Daily Bugle, Edward Brock (portrayed by "goddamn it, why didn't they choose ME to be Spiderman!" Topher Grace) is at the scene and becomes the new host to the symbiote, Venom.
Venom would have been a great "2nd villian" or heck leading Villian, but he is not even introduced until he is set to star in the final 4 way battle at the very end of the movie. 4 way, you ask? Yes, in another tack on to which they must have thought "well we had this really great Twist ending to Spiderman 2, we have to incorporate in SOMEHOW!" James Franco returns as Harry Osborn, who has transformed himself into the new, snowboarder inspired Goblin. His initial spat with Peter is way too long and the action is so much like the previous two films that it is almost boring to watch.
The story is mainly about redemption and forgiveness, with everyone forgiving everyone and redeeming themselves in the end. The editing seems very disjointed and there is no flow to the action at all. Not enough is explained and while it is understood to be a fantasy reality, it seems the viewer has to suspend reality too much to accept this could happen in the real world. (if its going to be this surreal, just do it all in CGI) At the end of the day it seems they had a 3 hour movie that they edited down to be 2.5 hours, when all they needed was a 2 hour movie, edited down to 1.5 hours just to wrap things in the series up. See it if you liked the last two, there is still some enjoyment to be had. But much like a spider on my shoulder, I have to flick this one down.