We have a mix of Mac's and PC's in a Windows Server environment.
I'm the admin, and my background is almost exclusively PC, with enough *nix to be dangerous.
My tenure started as the company was ramping up it's IT footprint, so I was asked as we added workstations if I cared whether the machines were Mac or PC. My limited professional exposure to Macs had shown them to be reliable, though I felt they were overpriced and that the user was excessively cocooned for my taste. I stated this as my opinion, and that if the company wanted to pay extra for comparable Mac's, I didn't care. I'm not an OS snob. All an OS is for is to operate software on a particular hardware platform. Nothing more or less.
Fast forward 18 months and we now have a brand new MBP that is pretty much a doorstop, when it's not in the Apple Store. It should have been replaced by now under Apple Care, but Apple isn't the Rich Uncle it once was, and now drags it's feet on hardware replacements.
[I'm familiar with Apple Care from when I used to work over the cubicle wall from the AppleCare people. We were all outsource workers.]
During the same period, we also had a MB go dead requiring a fresh OS install, keyboard failure on a desktop, and a dead display on another MB.
It's not a huge list of problems, but 100% of the issues we've had have been on new Mac hardware - both PPC and Intel.
None of the older units have had any problems at all.
I had wondered about the price decrease on new Mac's, and had assumed it was driven by Apple's desire to gain market share.
Now it seems to merely be a reflection of the decreased value of new Macs, given the higher failure rate and poorer quality of service and support.
I'll be looking long and hard at any new Mac additions to our physical plant, and if it's at all mission critical, we'll go PC. They may not be any more reliable, but they're a lot easier to fix and parts are easier to get and a lot cheaper.
We aren't a design studio, so there really isn't any advantage to Mac hardware for us any more.