Tim Bray waxes euphoric over Jython, and makes some broad generalizations about dynamic languages:

If I had to cram it into one sentence: it's faster to write software in dynamic languages, and the (real) benefits you get from an anally type-sensitive compiler can be had more cheaply with modern testing disciplines.

Of course, I have to disagree with Tim here, you can't get all the benefits of static type checking with modern testing disciplines. I've written about this misconception before, back when Bruce Eckel wrote about it, and that refutation still stands.

My guess is Tim's also comparing modern testing versus ancient static type checkers. Hey, Tim - have you seen what advanced statically typed languages are doing with the JVM? How about Nice, or Scala? They're both leaps and bounds ahead of vanilla Java, and definitely worth checking out.