I ran Linux for quite a long time before coming to Apple. I ran command line mostly and every now and then I'd mess with the gui. Gnome and KDE seem so much like Windows and the sys admin gui support was spotty when I tried it. Once I tried OSX and saw that clean uncluttered gui along with all the command line tools I knew and loved from Linux, I was sold. It was only a matter of time to put the funds together to make the switch.
There is also the matter of doing business with Apple versus M$. If I have a support question with M$, It seems like I spend more time proving I'm not a criminal than I do on actually solving my issue.
With Apple, it seems like the priority is to make it work as advertised or provide a workaround. With M$, the priority is to pump out a standard product and redirect end users to "solution providers" when they need help.
With Apple, the priority is on ease of use. With M$, as long as it is technically feasible to do something even if it's 25 clicks or involves a registry editing session, that's good enough.
With Apple, the software is provided as a means of making the hardware valuable enough to turn a profit. With M$, the software is the product and if you don't like it, too bad. You aren't the customer, the OEM that made the Windows box is the customer.
M$ has very little incentive to make you happy after the sale. I have never heard of anyone getting a refund from M$ for money they paid for windows. Apple has a customer satisfaction policy that I think is either 14 or 30 days. Whatever it is, it's 100% longer than M$.
Edit:
Oops. I forgot the biggest nail in the M$ coffin for me:
Vista. I was looking at new machines and I did not want to even think about paying for the level of hardware I would have needed to run Vista. And even now, after XP was supposedly taken off the market back in June, it is STILL outselling Vista. So says HP at least. Somebody needs to tap those folks up in Redmond on the shoulder and whisper...
Bullying,
lies and "Steer Manure" do not create good customer relationships.