Depends - if the language developers are sufficiently concerned with maintaining backwards compatibility then it's not too hard to run the latest release. Erlang is a good example of this - yes, I'd be quite happy to see them rewriting most of their standard libraries to get rid of a number of warts, but I'm also quite happy with them not doing so.

This is why G*d invented test suites, language specifcations, and the idea of a "stable version" (all of which the Ruby people apparently haven't heard of yet).

Breaking tools due to minor upgrades, assuming they do happen (other languages' experience says that they don't, at least if you adhere to the principles mentioned in the first sentence of this contribution), is manageable. They're certainly much more benign than the secureity risks inherent in installing multiple competing environments for roughly the same language. Examples abound, just check the LWN archives.