> Notice how smooth the 32-bit to 64-bit transition went? (and yes, it was smooth.)

I credit most of that to Microsoft and the insane efforts they make to support backward compatibility.

They made an extremely complex abstraction layer to run 32 bits applications on 64 bits OS, yet it works very well.

To this day, it's possible to run lot of applications that were written 15 years ago, seamlessly, as they were built and distributed 15 years ago.