Well, I guess some people see inconsistency in the vanilla textures. Could you provide notable examples?
Just compare early storage blocks, like iron and gold, to newer storage blocks, like redstone and coal. the latter are noticably more detailed, because they were textured by someone with a different style than Notch originally had. That's the same with almost every new block, that has more or less detail depending on the person who added that block at the time.