Like triumphant rock musicians who have never heard of Ravel and Satie, there are many successful Unix and Windows programmers in our profession with no experience of mainframes. Sadder still, they are convinced that mainframing is dead, and in any case irrelevant to our modern practice.
This is despite the fact that VMWare and the other virtualization software (and, incidentally, modifications to chip design to support same) are cribbed from forty years of virtualization experience on the IBM 370/390 architecture and the IBM Virtual Machine Operating System (called nowadays z/VM).
Oh, and did I forget to mention that mainframe sales are steadily increasing? And that their primary use in new installations today is to run multiple (say, 20,000) simultaneous instances of Linux/390 ?
Of course, not everyone has a mainframe in their basement. However, you can get free access to Linux running on an IBM mainframe.
Mainframes are fascinating if you are actually into software engineering and computer engineering. So much of the professional life of the modern Unix/Windows programmer consists of frantic pursuit of transient fashion that it is refreshing to take a dip in the deeper waters of mainframing. I mean, have you personally ever seen really mature software, software which has been polished over a span of forty years?
It's easy to scoff at "old software", but the reality is that this forty-year polishing period has been used to keep mainframing up-to-date. TCP/IP, Java, web services, etc., they're all there in the mainframe world. But they're only the top strata of a very deep and complex structure which entitles not only modern ideas, but also the ideas which preceeded those of the present day.