Since I have had 2 days now to mull it over, I give the film a grade of B. Its better than IM3, but beneath STiD as far as the summer sci-fi action films are concerned. My biggest issues are the pacing problems others have mentioned and that blasted first act jarring jump to current age Clark. I really feel like by pushing to combine Superman 1 & 2 they lost an opportunity to fully flesh out these characters and the universe we find them in before bringing in the Big Baddie of the Series - would have preferred a similar approach to what Nolan used in BB where Joker was teased at the end leading into an "Epic for the ages."
Not a bad film, but certainly not the great one it had the potential to be.