How Big Is VMS?

Is there any reason to use VMS today other than for existing applications that cannot be migrated? I've heard its reliability is legendary, but I've never tried it myself. The 1 year licensed VM seems excessively annoying. Is it just old and esoteric, or does it still have practical use? At least with Linux, multiple vendors release and support distros and it is mainstream, whereas with VMS, you'd be stuck with VSI.

I used it a bit at University - most notably it had an Occam system on it that wasn't available on the Sun workstations.

I'm curious about running a VMS system although the admin side looks a bit daunting. The thing I'd really like to do is run X-Windows on an emulator on my home lab, just to see it run.