About 3 years ago my company issued an edict that everyone had to use a PC. I managed to bootleg a Mac & now I have one of each on my desk.
Every morning when I turn on the PC there is a message that the IT department is going to "push" yet another update onto the PC. This always takes 5-10 minutes and maybe one day out of 5 requires a restart.
Now I turned the machine on because I wanted to use it, not update it. I guarantee you the company looses 30 minutes a week for every computer on this update thing. That is 25 hours per year. Given what they bill my time for, our customers should be clamoring to donate a Mac to me.
Real costs of professional employees are $100 to $200 per hour. You can not justify saving $500 to $1000 on a computer when you are going to throw away twice that much per year on lost productive time because of the choice you made.
And I haven't even begun to think about how much Sobig and Blaster cost us. Whole company email system down for several days. My Mac was immune to both.