It seems to be pretty much close to the speed of similar languages (python, ruby, etc). It loses a lot in the languages shootout[0], but that was back in January and its a very young language. It does seem to beat python in vector ops[1], so who knows what else it wins at.

Anyways, speed isn't the reason he is rewriting Io for the JVM - he wants the advantage of all the libraries already available, as well as being able to fix some small things he doesn't like.

[0]: http://shootout.alioth.debian.org/gp4/io.php [1]: http://iolanguage.com/about/speed/vector/x86/