Beautiful example how a combination of open source enthusiasm and commercial interest can generate some first class software. There's no way this could have happened without Evan's initial enthusiasm or Engine Yard's support. TBH I can list off dozens of open source projects that are one sponsor away from another level greatness. :P
You can also use jruby now. I'm not trying to diminish rubinius, I hope it works out well and I worked with one of the contributors, but I've been using jruby for a while now and it's great.
This is really great news: I spent some time digging around in the Rubinius JIT in December, and realized that it wasn't going to generate significantly better code until the byte codes were replaced with an intermediate representation that made type checks visible to the optimizer.<p>In the long run, Ruby implementations will be at least 1 order of magnitude faster than either MRI 1.9 or JRuby. And I'm glad to see that the Rubinius folks are taking the necessary steps to get there.
I've never been massively keen on the carious implementations of ruby, they're all a bit different and those differences appear to be documented poorly. This is most visible if compared to the python landscape.