Maven 3 Parallel builds

We upgraded to Maven few months back and recently tried parallel builds feature (I've posted about Maven 3 features in this earlier post - http://rajakannappan.blogspot.com/2011/07/maven-3.html.) in hopes of improving our build times. But, unfortunately our build times did not improve at all.

We are using the latest maven 3 version (3.0.3) and also the latest maven plugins available to date. Still, we get the many plugins are not threadsafe and so they don't take advantage of the parallel builds. For example, we get this during our build which shows these plugins are not threadsafe.

[WARNING] ********************************************************
[WARNING] * Your build is requesting parallel execution, but project
[WARNING] * contains the following plugin(s) that are not marked as
[WARNING] * @threadSafe to support parallel building.             
[WARNING] * While this /may/ work fine, please look for plugin updates
[WARNING] * and/or request plugins be made thread-safe.           
[WARNING] * If reporting an issue, report it against the plugin in
[WARNING] * question, not against maven-core                      
[WARNING] ********************************************************
[WARNING] The following plugins are not marked @threadSafe in 

[WARNING] MyProjectName project:
[WARNING] org.apache.maven.plugins:maven-pmd-plugin:2.6
[WARNING] org.codehaus.mojo:cobertura-maven-plugin:2.5.1
[WARNING] org.codehaus.groovy.maven:gmaven-plugin:1.0
[WARNING] org.codehaus.mojo:buildnumber-maven-plugin:1.0
[WARNING] org.codehaus.mojo:exec-maven-plugin:1.2.1
[WARNING] ********************************************************

It is unfortunate that these plugins don't support running in parallel even though Maven3 is out for a while now. Just posting my experience and hope it changes soon...