You can certainly just call JRuby directly with the 'java' command, or just set your environment to point at the Java 7 install only when you need it, rather than forcing your whole environment to use Java 7 by default.
I imagine the computer benchmarks game will update when we have a release of JRuby 1.7 out, sometime early 2012. If someone else wants to do some benchmark runs, I have no objection.
As for Clojure and Scala...they may see modest improvements from Java 7, but neither of them use invokedynamic at all. The biggest boost for JRuby comes from invokedynamic.
I imagine the computer benchmarks game will update when we have a release of JRuby 1.7 out, sometime early 2012. If someone else wants to do some benchmark runs, I have no objection.
As for Clojure and Scala...they may see modest improvements from Java 7, but neither of them use invokedynamic at all. The biggest boost for JRuby comes from invokedynamic.