I updated my Ruby 1.8 vs. 1.9 benchmark.
It seems they continue to speed up Ruby in the latest 1.9 trunk, eliminating some slowness and stabilizing the new VM.
For the projects I am programming lately, namely Fukubukuro (a JavaScript interpreter in Ruby) and EPIC/EVIL (a secret project ;), Ruby 1.9 turns out to be about twice as fast as Ruby 1.8.6. I also profit from faster testing, spec-checking and RDoc generation.