I have found couple little problems causing multi-module incremental build not to work as excepted. The changes are localized in hudson.maven.MavenModuleSetBuild.java under mave-plugin

1 - isDescendantOf does not normalize the path being tested against normalized mod relative path
2 - belongsToSubsidiary have the same problem with path not being normalized and in theory should simply delegate to isDescendantOf (with minor common code extraction/refactor)
3 - startsWith fails in cases where there are same level modules with the same name prefix. e.g. a change in any of (utils, UtilsIO and UtilsNetwork) will always trigger utils module.

I have experienced issues 1 and 2 when using Hudson and SVN "Local module directory" and AccuRev @Sub-path". Both scm providers returned changes using / separator while Hudson maven modules getRelativePath() returns paths with \ separator. I believe the problem might present in other providers.

Issue 3 is a specific to certain use cases and I suspect will not bother a lot of people.

PS I am amazed by the code quality that goes into Hudson. If nothing it is an example of how software should be written.