I just finished this game.
As a vet of the whole series (1, 2, 3, and Ultimate) it was clearly the most refined of the 3, and lots of fun, but (as with the others) short of greatness.
Swinging is so intuitive and freeing that it's hard to fault it, though I still can't quite recapture the glory of swooping through Midtown in SM2....maybe because it's the second time around so there's not the "woah" factor. I think it's missing the feeling of speed a bit though....I'd like a slightly faster max speed.
Bosses were what you'd expect. It's obviously a mixed-market game, so it will be easier than those which target hardcore gamers.
The biggest improvement was on the missions themselves, from the small crime-stuff to the main story. Repetition was noticeably less, and the scenarios felt more fresh than in past games (balloon grabbing, anyone?). Even the (occasionally frustrating) button-timing sequences were suitably epic, with Spidey performing some crazy and entertaining maneuvers.
The writing and voice-acting were sub-par and/or phoned-in. After Ultimate Spider-Man, which had superb production value in these areas (but insanely formulaic bosses) this was a bit of a letdown writing-wise.
And 1 mission as Harry? Only 1?! Wtf.
Good for fans of the series, or of Spidey himself....if nothing else, for the swing mechanics and free-roaming, though the whole product is entertaining as well. Not a must for others though.