Migrate an all Mac design shop to a PC environment? Challenges?

Hi! I have a 5 person in-house design shop all running on Macs an with a 10 year history of doing great work for our company and our clients. Our new CIO wants to migrate the entire department to PC’s. Server and all. I have a definite opinion about this, but I would like an objective point of view. What are the challenges I would face in equipment, time and software?