Maybe it's just the lack of a corporation pouring billions into it like google did with V8, but I suspect that ruby can never be fast, due to ObjectSpace and the like. That awesome/insane object model we all like so much is just impossible to optimise. All the other weird shit ruby can do doesn't help.
http://blog.headius.com/2012/10/so-you-want-to-optimize-ruby...
Still, for stuff that doesn't need to be fast, ruby is still a joy to use, and always will be. The enumerable API feels so fluid, it's only really surpassed by languages like clojure in my experience.
As you might be able to guess, I'm looking forward very much to swift becoming a general purpose language. If apple are all funny about it and try and neuter the ecosystem for some reason, I will be a sad panda.