For this job, it wasn't a problem. Because honestly 60% of my current job is business analysis and documentation, dealing with customers and end users, etc I was able to emphasize that part of my experience and de-emphasize the VMS. They did insist on someone with a development background, but didn't seem to care much what platform the development took place on. So here I am!
It did seem to be a problem for nearly all other jobs I applied for, though. It seems like companies could always come up with some excuse... "we want someone who's been doing business analysis 100%", one place felt that my work (with near-realtime critical systems) wasn't technically challenging enough to prepare me for a job with their hallowed group, and the ever-present "not a good fit". I even applied to several OpenVMS jobs and was told I was not a good fit. I think it was actually just that I wasn't local.