No, please no!! Not another apple in the bussiness. Things are good as they are now, for me +1.
The idea that Apple already requires you to run their OS on their hardware is a bad deal for consumers. There is no real choice there, and you can't build your own and install Apple's OS on it without violating their EULA. You are stuck with whatever they want to offer you, at whatever price they decide, and often inflated prices at that.
Do we really want another hardware dictatorship telling us we have to buy their overpriced hardware in order to run Windows?
Microsoft becoming an OEM will take that choice away from Windows users and take Windows away from the ones that like to build their own machines.
One of the great joys of being a PC user has always been choice. You can drool over hardware and plan your dream machine, build it and then install the PC OS of your choice...Windows, Linux, BSD, etc (just about anything except Apple) then all the software you want.
You could choose from many prebuilt machines, of many brands, and many specs and purchase something suitable for your purposes and budget.
If you didn't like the last HP you bought, you could go with Dell next time, or one of many other companies. Or a college kid that builds PC's in his basement for extra cash to help himself get by.
If Microsoft became another Apple, where would you go if you didn't like the last Microsoft machine you bought, or their customer support, or some other issue, yet still wanted to run Windows?