I enjoyed this movie, not as much as the previous two, but still had a thrill watching it. For those of you expressing disappointment at the "dark" tone, its fairly obvious you've never read the Spider-Man comic books, or you'd have expected it as soon as you saw the black suit.
**SOME SPOILERS AHEAD**
This was one of the darkest times in Spidey's/Peter's life. The symbiote made his relationships with everyone (friend and foe) on edge, and he had some serious anger issues. Of course, the movie kind of flibbed his relationship with Gwen Stacey, as she was his first love before MJ. In fact, the scene from Movie 1, where Green Goblin tosses MJ off the bridge...was actually Gwen in the comics...and she died. That guilt still haunts Peter to this day.
I thought the special effects were awesome, especially on Sandman! And I was glad to see some good team action, since that's been missing from most Marvel movies with the exception of the horribly lame 3rd X-Men movie. Marvel is all about the team ups, and this movie pulled it off beautifully.
Personally, I think this should've been the 2nd movie in the trilogy, kind of an "Empire Strikes Back" thing, where the bad guys win a little, and the hero doesn't end up with the girl. Then the third could've had Spidey/Pete defeating Venom and Doc Ock and getting straight with MJ at their wedding. But that's just my opinion.
**END OF SPOILERS**
Anyway, those are my thoughts on this movie. Good, but not great. In general, stuck with the feel of the Comic, as Spidey has always been about the Cheese and the Darkness. Loved the emo cut.