JRuby is fast for a Ruby implementation, but it's still far, far slower than Scala or Java itself.
http://shootout.alioth.debian.org/u32/benchmark.php?test=all...
http://shootout.alioth.debian.org/u32/benchmark.php?test=all...
But citing the Alioth.Debian benchmarks? Really?
Dude, take a look at the source-code of those benchmarks sometimes -- they are completely useless ;)
Say what you think is wrong with the source-code of particular programs.
You think the Ruby code could be faster, and thus the comparison is skewed? Go ahead and help everyone understand by improving it.