Richard Monson-Haefel has this to say about Groovy:

The hype surrounding Groovy has died down and buzz about the project has been pretty quiet and in my opinion that’s the best thing that could have happened. The result is a language that has had time to be developed into something that is going to be truly useful. In many respects Groovy is the best combination of the Java platform and dynamic language design. Groovy has been quiet, but like a sleeping giant Groovy will awaken and effectively take over as the dominate dynamic programming language after it becomes a JCP standard.

As he correctly points out, it doesn’t really matter that much whether Groovy is as good as Ruby, or Python, or any other language — its (perceived or real) roots in the Java community might actually turn it into a great success, regardless of its shortcomings.