To me, the hair wasn't an issue, really. There are a few points that don't make sense (and the hair issue is an age old one, I seem to remember similar comments regarding Christopher Reeves' hair), like, during the main fight scene, on SmallVille's high street, the US Army fire a missile at the Kryptons, lead by Zod. This missile explodes, all the superheroes/villains are still alive AND all the shop windows are intact!