Ruby VM's are not interesting. At least not to me. If you want a VM like the JVM, just use the JVM, you will be much happier in the end and maybe get to enjoy life more. Creating a faster/multi-threaded VM is a good learning experience, but does not mean much even in the short term.
Ruby does nothing for software safety than any other imperative computer codes. Although Ruby "makes programmers happy", this does not mean a hill of beans in improving our customers lives. If happy programmer == well-tested code that meets the specs, then great. But as Obie Fernandez points out, this is not frequently the case. Living the 80/20 rule through a world full of broken code stinks. I really like some of the research going on to allow Ruby to make applications that more concurrent, fault tolerant, and still be, well, Ruby. I hope some of these things make it into Rails Conf next year.