I don't mind the youth of the actors. I did at first, then I went to the San Diego Comicon where Singer talked at the panel there. A fan asked the same question, "why cast so young?"
He basically answered that when you're planning to do a new series of movies, its good to cast them young so they're not so old by the time you hit the third film or whatever. Kate maybe young, but as he said, "she's playing the character older". I thought about it and I agree with the decision. Remember how weathered Margot Kidder got by Superman 3 of the older series?
But as far as negative things:
-I think the "S" symbol on the chest still looks too small.
-I think the red should've been as bright as the blue and yellow. The reason why it worked previously is because all 3 colors balance each other, now....1 of the 3 is darker and muted and throws off the trinity of colors.
-I'm not too keen on the seams on the arm and such ...but that's no biggie really.
-I'd still like to have a black haired Lois Lane instead of a brown haired one, but that's also very small minor thing for me.
Mainly the "S" symbol and the darker red is what I really don't like so far. The rest of the movie better be really cool to make up for this .... in my view.