Java Build Tools and Future

It's always interesting to read comparison of Java build tools. There are two major player so far: Ant and Maven. But, I'd like to know more about other tools. 

Here are some interesting links: 

• www.hjug.org/present/Java_Build_Tool_Comparison.ppt - short comparison matrix, it's really useful for overview
• The future of Java build tools - conceptual review, worth reading, especially comments
• http://java.dzone.com/news/maven-or-ant - pros and cons for both Maven and Ant
• http://www.webforefront.com/archives/2009/09/java_build_tool.html - small Maven criticism
• http://kent.spillner.org/blog/work/2009/11/14/java-build-tools.html - "Java Build Tools: Ant vs. Maven", I think it's really famous article in the Internet. Just read arguments of Maven hater.
• http://community.jboss.org/wiki/Gradlewhy - Hibernate moved from Maven2 to Gradle!

Top 3 Java build tools:

• Ant + Ivy (http://ant.apache.org/)
• Maven (http://maven.apache.org)
• Gradle (http://gradle.org/)

I don’t want to mention the other tools. The list isn't small. I'm not sure if it worth spending time for learning/investigating new build tools. We should follow the trends.

Ant and Maven are good enough for any projects. But Gradle evolves really quickly. So, we can get additional "big" player on Java build tools field.