The simple reason behind Mikeysoft making Vista is because they can, and they will also makes lots of money from it. My Dad currently has the vista Beta 3 on his desktop I personnaly think it's the best OS I have seen yet. Although it does seem thats its main upgrades are just on graphics.

And I dont think they are "trying" to look like apple, I think they are trying to look more stylish and with apple being the best looking OS out there it's likely there will be some similarities.