Hi Lasse: Jython's viability as a language has been in question for a long time. It seems to be a recurring theme. I chose Jython as the TestMaker scripting language two years ago and I've been happy with the choice.
The Jython project runs two email lists (jython-users@lists.sourceforge.net and
jython-dev@lists.sourceforge.net). All of the questions I have posed there have been responded to by other users and the maintainers (Samuele Pedrone, Clark Updike, and others.
The developers are working on Jython 2.2 that will incorporate several changes that have happened on the Python side over the years.
The most impressive thing to me about Jython is its stability. I have run complex scalability tests of Service Oriented Architecture (SOA) with up to 20,000 concurrently running test agents written in Jython. Jython is solid.
Groovy looks just that: it's groovy. I like the fact that Groovy compiles into Java byte codes. This is VERY important to the Java community as it puts Java on a better competitive footing with .NET's ability to run multiple languages through their VM. Please
read my blog about Java and scripting. The biggest problem for Jython and Groovy is Sun's reluctance to endorse scripting and to support it.
-Frank