About 60% mac users, I dominate locally via SEO and a lot of other companies around here say they "don't do macs" which brings me clients.
The difference in servicing macs / pcs is night and day.
I hate servicing windows machines, I should charge more but I do them to keep the income in. Windows machines always have viruses, malware, problems galore. No machine is the same. This comes with the entire market thou, with so many different manufactures, spare parts, etc...
Macs are great. I now know to fix any imac or MacBook Pro, and because I'm focused on that, there's not much variance, and it becomes a well oiled routine. Migration is dead easy, time machine will move data over from another hard drive or backup with a few clicks. It has never failed on me. Upgrading the operating system is dead easy, just run the installer from boot and point it at the hard drive. It works it all out for you. No need to worry about moving data over windows vista to windows 7 problems, blah blah blah...
As for using them, I have them all in my business and home life. They are very reliable and take a beating. Managing them is easy. Networking them is easy (to have a look at OSX Server, it's child's play). Every client I've ever spoken to says they'll never go back to windows. It's that simple.
Oh, and if you think macs are for just the artsy type crowd, you're sorely mistaken. Off the top of my head : building safety auditing business, retired handyman (ok he used to be in advertising) , farmers market conglomeration, at home mums, sole parents,tradesmen...
And don't get me started about Windows 8. Oh my god I'll never hear the end of it from clients, Microsoft just lost the plot in that one!
Lastly, mac clients are much better then windows clients in terms of $$$. They've spent good money on a computer (remember those days?) so they don't freak out over a $300 repair. Compared to windows users who penny pinch and have no idea what the real value of their computer is (data, work, software). Mac clients just say "yep" because, well, they have to be in a good financial position to buy one in the first place!