Currently I have a 24-85mm lens. Its at the 85mm end that I feel I don't have enough rather than at the beginning. I sold my old 18-55 kit lens to get the 24-85mm. I have not missed the 18 too much. Therefore I think I should be OK. If I really need something wider, I could get a wide prime for it perhaps?
As for the Canon vs. other manufacturers, I'm just trying to see which will give me bang for my buck I guess. The lenses are not cheap, especially when your a student hehe.