... with spoilers
The movie exceded my (modest) expectations - I think Poland's review was more or less dead on, except for this: the movie managed to work anyway.
The biggest problem I had was with Bosworth's Lois. I actually thought her performance was much, much better than I expected, but the character still didn't work.
Some of this was for the reasons others have pointed out - she's just too damn young. I never for a second bought her as a Pulitzer prize winner. She's too young and too insubstantial.
The script didn't help her out here. What's the first thing we see her doing? I think we're supposed to think she's asking a tough question. The answer (something along the lines of "that's in your press packet") however, tells us something different: she's unprepared. Her followup question about TV networks is no better - it makes her look like a ninny.
That whole sequence is the weakest part of the film. So all the power goes off everywhere, and then comes back on, and the plane is fine (um ... ok) except the countdown won't shut down? The incredibly complex, designed-to-be-easy-to-abort launch sequence won't abort? Um ... okay. Everything else works, but that. Oh, wait, and the bolts, which somehow get stuck.
... right. So everything comes back to normal 100%, except for the two systems, which fail in completely opposite ways, which would create the disater.
How stupid do they think we are?
Not as stupid as Lois, evidently. While everyone else is putting on their air masks, she's taking off her seatbelt. Why, exactly? Are we supposed to think she's helping someone? Okay, everybody who's ever taken a commercial flight can answer this question: if you have to assist someone else with their mask, do you do it before or after your own?
That being said, I actually thought Bosworth was good in the scene with Superman when the script wasn't making her act like an idiot ("Oh, I'm going someplace so dangerous i don't want to leave my son in the car ... but I'll just leave my cell phone here and NOT answer the call telling someone where I might be.") or get hit on the head.
And the first real action scene (the plane and the shuttle) never really takes off. You never feel that there's real risk.
The miraculous thing to me was that the film recovered from a really abysmal first 30 minutes or so. The imagery is iconic enough, the action scenes (that one excepted) well shot enough, the music starts swelling ... I fell for it. The movie won me over.
Routh was fine, but unspectacular - which was all that was asked of him. Spacey was good. I thought James Mardsen was an uninteresting choice. Bland. Good looking. But no attempt was made to explore what he meant to Lois: is she simply going for the most superman-like guy she can find, a convenient alpha-male type, or maybe going for the anti-superman? Any of those would have been plausible choices - but Singer & co simply didn't make a choice.
I had plausibility issues with the ending. He's so wounded he can barely stand up - but he can still lift the damn thing into the atmosphere. Granted, this is no sillier than some of the stuff in the Donner films (spinning the earth backwards, suddenly being able to teleport and project visions of himself) but seemed like a cheap way out of the nice corner the filmmakers had spent so much time painting Superman into.
I also would have liked to find a way to connect the emotional stakes with the action stakes. The first Donner film did this well with the two nuclear missles, forcing (aparrantly) Superman to make an aweful choice. In this film the emotional story and the action story never touched each other. Heck, they didn't even make eyes at each other across the room.
But the film's greatest asset is that, despite all these flaws, it basically works. It catches you up and takes you on a pretty fun ride. The parts don't really add up, but the whole is more than the sum regardless.