I AM FILM GUY has a good article on moving from Mac to HP.
I still worry about articles like this as it seems like they may be payed or getting gear for free (you can never tell), and they never go into the OS differences of moving from Mac to Windows, but you never know. I have been seriously considering the switch because Windows machines are so much newer and CUDA support so much better.
I thought about a Puget Systems custom system though.
Who knows, maybe the next MacPro will change my mind, if it ever comes out.