Folks, its a trade off.
I am an IT Consultant. Most businesses run PCs because thats what the software they need runs on.
For my clients who make the Mac choice, they have limited applications. For the businesses that are really only doing correspondence and bookkeeping (and media work of course) I recommend Macs as their first choice if they can afford the upfront higher purchase costs. Most of my Mac offices are "set and forget" with very very little ongoing maintenance needed, with the exceptions of hardware failures, which happen at a very low rate, about the same as the rate for PCs.
For my customers who must run some line-of-business application that requires PC, or they cannot afford the much larger up-front costs of implementing a Mac solution, they get PCs. They experience about the same rate of hardware failures as Mac customers.
On an ongoing basis (once the office system is implemented) the PC networks require much more ongoing maintenance. This is mostly the fault of malware and trojans and end users doing something other than work while at work. I make much more money in the long run off of a PC implementation simply due to malware, and I tell my prospective customers this UP FRONT. It usually raises quite a few eyebrows to admit something like this, but it drives home the point that its either money now or money down the road. Most businesses choose the PC route. They seem to like the gamble.
The Mac clients sometimes get very upset that they cannot try out alot of the software they see without putting a PC in the office. But that seems to be the price of stability. OSX is relatively more stable, but as I see it, only because the configuration in a working office of Macs is just as stable. I know when I see an office user with (pc) all those games and web content downloads that I will see them soon for a service call. Contrarily, when the office listens to me, and keeps all that crap off and simply works on their pc, not downloading crap all the time, their stability is relatively equal to the mac.