I suppose it depends on what you're using ruby for. I use it for long running processes like rails apps so the jvm startup time really doesn't matter. And jruby has support for c extensions that use ffi.

The second is actually much less painful than people generally think. Jruby -e 'some code' only takes half a second on my machine, which is fast enough to not be a problem. The main slowness people experience has to do with loading gems, usually via rubygems. That is painfully slow, but does not have anything to do with JVM startup time.