Just a month ago, Antonio Cangiano ran some benchmarks against a Ruby 1.9.1 preview versus several other Ruby interpreters. Ruby 1.9.1 clocked in at at least twice as fast as Ruby 1.8.7. This is great progress and will tone down some of the "but Ruby is slow" type arguments that have gone around, even though in the grand scheme of things it barely makes a dent.
I don't care much, but doesn't it bother people that it was so simple to make Ruby twice as fast? It must have been terribly inefficient before. All the wasted CPU cycles with all those sites running Ruby on Rails applications. Energy wasters.