Both Apple and MS have been doing that for a while. MS got me when they came out with MS Word, which opened formats from just about every other word processor - Wordperfect being the main one. Apple got me when they introduced Bootcamp and I was able to run both OSs on one machine. Slowly but surely it got to be a pain to keep booting back and forth and I switched to OSX.

I'd imagine it's a similar story for a lot of us out there, just different apps, libraries, dev tools, etc, luring us back and forth between the various operating systems. I wonder if I could be lured back to the MS side?!