I agree with needing more data but I will give my testimonial. I switched from Windows 7 to Mac Lion several months go and have not looked back. Simple things like responsiveness of the touch pad, gestures, and a better terminal are definitely what got me. Overall I would say the UX is just simply better.
The change in responsiveness in the UI when you're no longer using the trackpad is astonishing. It takes me longer to perform tasks on my Mac than it does on my Windows 7 platform - particularly if that task involves switching between windows in the same application. The loss of my extra mouse buttons to move backwards & forwards on web pages has been especially painful (though oddly, they work to bring up Mission Control & the Application window controls)
And frankly, after using Mintty from Cygwin, the default terminal on the Mac was pretty terrible to use. Fortunately, that was easily remedied with the use of iTerm.
I'm looking forward to the time I no longer have to use a Mac for work development.