I agree with CWP, but I'd like to add a few things too. Also, spoilers.

I felt the plot was a little too convenient. Like Peter's dad just happened to work with Dr. Connors at Oscorp, who just happens to be the bad guy and Gwen just happens to be his assistant. Also, I wish there was more Spiderman in this movie and less Peter Parker because I didn't like him all that much. Garfield is a talented actor, but I just didn't like the character too much. I also wish they had handled Connors better. They tried to make him sympathetic, but didn't do a very good job of it and his Lizard arc just seemed rushed. It would have made more sense if they'd handled the character of Dr. Connors better, either making him more villainey as a character or explaining that The Lizard ego made him evil somehow. Personally, I think it would have made more sense if Connors was dying instead of Norman Osbourne and that drove him to create the Lizard serum to cure himself. That would have made more sense than a lost arm, which btw they never explained how he lost or if he was born with it or what, and would have given him more depth because injecting the serum into himself would be a more primal survival action, as opposed to just regaining a lost arm. That may have set up something interesting, especially with the antidote at the end. Connors could have gone through a morale dilemma, like what price would he pay to continue being alive, even if that meant him turning into the Lizard and letting that destructive ego take over.

EDIT:

Oh yeah, a few final gripes. Why did they have to do those first person shots? They were terrible. I mean, if there was something interesting happening in them it would be okay, but there isn't. It feels hollow and gimmicky. Also, how does shooting a web onto your leg make a bullet wound just go away? That's ridiculous!