Better late than never:

<code>[david: rspec (master)]$ multiruby -S rake spec
...
Passed: v1_8_6_114, 1.8.7-p72, 1.9.1-p0

[david: example_rails_app (master)] $ multiruby -S rake rspec:pre_commit
...
Passed: v1_8_6_114, 1.8.7-p72, 1.9.1-p0
</code>

Coming soon to a gem release near you.