I'm a Microsoft Training Consultant and work from home developing training courses etc for MS.
I have a Windows 7 Laptop (although this never gets used). All of my work is done either on my iMac or my MBP. Everytime I give a presentation it is done using Keynote, as I prefer it to PowerPoint.
As far as I am concerned, Apple just make better systems! (Although that is not my
professional opinion of course!