First of all, in the movie he was a Brotherhood lackey, so the whole cameo thing doesn't work. If he would have just been going to collect Rogue for Magneto and that was the last we saw of him I could understand. But he was in every scene with the Brotherhood and was given a spot to be characterized. The Sabretooth they created in the movie was not just Logan's rival and his alone, he was taken too far into being a part of the Brotherhood, which I thought was a mistake. If they had kept him mercenary style, it would have avoided having to give him any true character because he really would be just following orders. But they didn't, they made him a *****.
Also, they did good with Magneto, but they really did diminish Mystique, if for no other reason than the ******ed ass scales on her body. It kinda ruined the whole seductive look she had before that was portrayed because of the crusty skin they gave her. *vomits*