Probably not too many spoilers here. (If you don't mind spoilers, this scene-by scene hand-puppet version is quite fun). And this is someone else's much better prose version of this page.

• spider-man was just peter parker in a mask, i.e. a wimp the whole time. this is supposed to be a hero who hangs around (sorry) with Blade.
• sticking true to the original storyline was all very respectful, but they forgot that the original storyline wasn't very good. lest we forget, the original spider-man comics really really sucked. they had an exclamation mark in almost every frame. originally, spider-man could use his web for skiing. they don't need to introduce the character these days, and certainly they don't have to stick too rigidly to the geeky teenager era of spider-man that was designed in a very patronising way for teenagers, in which he would foil a robbery every episode as a major plot device. they should have gone for the settled-into-the-bugle-job spider-man. having said that, I liked maguire as parker generally, despite his squeaky-cleanness.
• mj actress (kirsten dunst) sucked completely, and had nothing to do with the original character (since the original character didn't have to do much except be admired from afar).
• there were no shots of spider-man looking cool.
• no lighting, or rather, darking. times square scene in the day was a fiasco as a result.
• the green goblin's costume sucked.
• (defoe himself and the younger osborn both ruled)
• the fight scenes were incredibly dull
• spider-man didn't do anything cool
• there were no spidey trademark wisecracks (except one to jjj, which sucked)
• there were no quotable lines, except the mogwai one
• many parts of the dialogue were dire
• basically the whole thing was screaming "scene-setting pre-(cash-cow)-quel"
• compare it to e.g. Superman (1978) for how to get both plot and characterisation into one film (many aspects clearly based on Superman but almost always less well done)
• far too many shots of people's skeletons made suddenly visible. what the hell is it with cg artists that they need to do that in every film?
• spider-man's costume is not the same as on the hype posters. since this is the only thing (other than buildings) on the posters, I'd say that's a "give me my money back!" misrepresentation. fortunately, it's better than the hype posters, at least on the eyes, but that's not the point. given that the posters were brought out at least a year early for hype reasons alone, they could at least have settled on a costume design by then. it's just disrespectful of the audience.
• the eyes on spider-man's costume were far too small, though it's good that they kept them white-with-border (unlike the posters). the costume should have had the added black that the comics spidey has these days. admittedly, there's the problem of how spidey gets a decent costume, since it's never explained in the comics either (roll on, venom).
• spider-man had no presence. batman can stand still in front of a camera for hours and look cool, but when spidey's standing still, he just looks a bit silly and uncomfortable.
• when osborn hurriedly leaves the thanksgiving meal, there's no clear idea what he's going off to do. hunt down every cycle-messenger in New York?
• much of the sfx was very bad, such as the jumping-between-rooftops scene. straight out of the matrix, but without the effort.
• warning - anyone who told you the plot is "dark" may be comparing it to "sleepless in seattle". the original comic is dark (at some point, maybe after stan lee let someone else do the writing?).
• spider-man looks like he's wearing pyjamas most of the time.
• did I mention that all spidey-v-goblin scenes were incredibly dull? they were.
• also, keeping parker's voice was a mistake. spider-man really is an alter ego, and has an associated sarky voice which maguire's squeaky voice fails at miserably. a large part of spider-man's appeal is the banter, which is utterly missing. schumacher (spit) would at least have got this right.
• blatant product placement, natch. I include macy gray in that.
• gratuitous wet-t-shirt shot of dunst. it's just totally out of character. you don't put in a wet-t-shirt shot of the gril next door. especially since she appears to be utterly oblivious of the fact. if you want to see how women react to wet-t-shirt situations, see "as good as it gets". actually, see it anyway, it's an incomparably better film.
• j. jonah jameson isn't scary enough.
• i have no idea how it is possible to make a film with bad dialogue these days. how hard is it to apportion 0.1% of the film's budget paying someone to edit dialogue properly? just say "your job is to make the dialogue not suck. kill script-writers if necessary."
• poor sets in times square and ending fight scenes.
• final green goblin fight scene ends very boringly.
• mary jane too fat (her basic morphology, comic mj is tall and thin) and not at all like the original demure character (this one grins inanely at everything)
• the city had no atmosphere.
• did mjw know she'd lived next door to pp the whole time? pp's early chat-up practice scene (mmm cliche) suggests otherwise, but she shows no surprise when she notices him across the fence.
• parker grinning at some graduation ceremony (cliche), apparently the day after his uncle has died.
• parker utterly remorseless about murdering uncle's murderer.
• the upside-down snogging is risible. and they could at least have edited out the stubble.
• the webbing is thin and weedy. realistic, maybe, but uninspiring.
• the scene where parker comes down the stairs and briefly wall-walks is good.
• the bridge scene is both cliched and dull, leaving spider-man completely prone (again). in fact, in general, the goblin runs rings around him. unsurprising really, given the goblin's firepower.
• spider-sense massively underplayed. could have done with more matrix/predator-style. ditto spider-strength.
• most action scenes sorely lacking in wire-fu. this is a character whose defining characteristic is being able to walk up walls. now think of the opening trinity scene in the matrix. more of that, please.
• The Raimis should be concentrating on bringing back American Gothic anyway.

You'll probably like it.