Not bad, but a bit of a mess. First and foremost, there is an allegory in this picture. The Venom-suit (that I recall, it was never referred to as such, but who cares?) enhances Spidey (Tobey Maguire)'s powers and gives him an attitude problem. It becomes an addiction he needs to learn how to kick.
Okay then, let's start with the black costume. From a visual standpoint, I wish they'd patterned it after the comics, but it works well enough here. Anyway, the costume comes from a meteor which just seems to hit while Peter and Mary Jane (Kirsten Dunst) are laxing on a web-hammock in the woods. Nowhere does the screenplay address where it comes from, nor does it play to the idea that if this meteor fell from the sky to Earth, that might have intrigued people. It's just kind-of off-putting (even to many people who DO read comics) that it shows up as if symbiotic alien blobs of goo arriving on Earth is a day-to-day occurrence.
Then there's the costume's vulnerability to sound. The idea that Parker discovers its weakness by accident while banging on a Church bell is one thing. The fact that he's banging on it in the first place is a little too contrived. Prior to this, there were scenes of Parker talking to Doctor Conners about the properties of this alien thing... they had the opportunity to actually SAY it is effected by sound, and they blew it. As for Venom himself? Well I don't know whether to blame the actor (Topher Grace), the script, or both; but Eddie Brock/Venom comes off as a dandy.
So what is it exactly this "costume" does? Well, it wraps itself around Spider-Man's costume and it enhances his powers. Unfortunately, it also makes him more aggressive. Upon learning that a villain called the Sandman (Thomas Haden Church) was the real killer of his Uncle, the suit increases his aggression to the point where he decides to murder Sandman once he finds him responsible for another crime. He kills him--or so he thinks.
It doesn't just effect Spider-Man's ability to be tough on crime. It also makes him more aggressive toward Mary Jane. He actually talks the other love interest, Gwen Stacey (Bryce Dallas Howard) into going with him to a jazz club, where MJ is employed as a waitress/singer. He (somehow) gets on stage to play piano while she's singing, then cuts a rug. Then, he gets in a fight with the manager and security of the club, and hits them (and MJ) before realizing he needs to ditch the suit.
Sounds like a lot going on? That's not all! There's also the matter of Peter's former friend, Harry Osborne (James Franco), whose father was the Green Goblin. Early on in the film, he attacks Peter (both literally and figuratively) out of the blue. The altercation between the two of them leaves Harry unconscious, and he looses his short-term memory. Because of this, he doesn't remember that he blames Peter/Spidey for the death of his father, or even that they're the same person. Eventually, he DOES get his memory back (through a borderline-absurd sequence of events) and threatens Mary Jane into leaving Peter, saying there's "someone else." He then tells Peter that he is the other guy and eventually lures him into fighting him. This ends with Harry lobbing a pumpkin-bomb at Peter, which Peter throws back at him.
When we see him again (Pete just casually shows up and asks for his help... no, really) it makes no sense, because anyone watching this would have thought he was killed in the blast. Oh, sure, this is a superhero movie, and we need suspension of disbelief, but they could have at least SHOWED US BEFORE HAND THAT HE LIVED. They could have had his manservant save him from a pile of rubble, or had a "my face! My face!" scene. A little common sense! He tells Peter to leave. Then his butler convinces him that Goblin Sr. did die by his own hand. And so while Spidey is battling Sandman and Venom once they finally team up, he appears to aid him and Mary Jane.
Howard's character is somewhat overused. They try to use her character as an anchor for a lot of things... and in some cases, it's not necessary. There really wasn't a need for her to be Brock's girlfriend. It didn't add that much to his character or hers. Did they really need her to be the damsel he saved and who kissed him?
And as usual, the humor becomes a tad stale after a while. There are some--as was true in the others--which fall into the dreaded "camp" category, such as the Jazz-club scene, or the scene where he walks down the street with his collar up (parodying Saturday NIGHT FEVER). A lot of this comes off as self-indulgent.
Okay, so with all the negativity I've lobbed, it may seem odd that I'm not giving it a low rating. Well, for starters, I can't review it without referencing SUPERMAN RETURNS: a far worse movie that gave us a flaky deadbeat dad and said, "this is supposed to be SUPERMAN!!!" But also, there is plenty of good in it.
For its untanglable web of a story, there are many worthwhile scenes. Having said that their brand of comic-relief does get old after a while, the Daily Bugle supporting cast (J.K. Simmons, Elizabeth Banks, et. al.) are as good as ever, as is Rosemary Harris as Aunt May. And Spidey-newcomers Howard (daughter of the legendary Ron Howard) and Church bring their characters to life in a way that will please fans of Spider-Man (I mean, the three or four who haven't seen the film). They resemble their characters visually. Plus, Church is sympathetic, but tough; and Howard comes off as smart AND alluring. And while the special effects are still not perfect, the action sequences are mile-a-minute when they're there and certainly worth seeing.