I guess the real reason for a scripting language programmer to go Java is that you want to use the JVM?

Otherwise, wouldn't it be simpler to just profile to find the slow places in your existing code -- then rewrite those in C? You can use the scripting language for most code, where it shines -- speed of development. And still get a good speed of execution.

If you need even more speed (you wouldn't really get less memory usage!), then sure... Java is one way to go for a Python/Ruby/Perl/PHP guy. But... when is it the best choice?