Dunno if it's been said yet, but I think Tom Welling (Clark Kent on Smallville) had contractual obligations that prevented him from being in the movie. He would've done a great job, though, yes.
This guy...I dunno, he doesn't look very superman-ish, but maybe it's just the poses they've got him in. I don't mind the costume much; besides, superman was never about the costume, but more the man inside the costume.
Guess we'll just have to wait and see.
As far as the storyline, I think I remember hearing that it goes something like this: Superman was away from earth for however many years (5-10 maybe?), has come back, and is seeing what the world's been like now that it's had to move on without him.