I've also found this to be the case (using the latest eclipse 1.5 plugin)
Having taking a look at the plugin template which generates the .classpath, it's obvious that this property is not used at all.
I've changed my local copy of the classpath.jelly file to include this:
<!-- iterates through each comma delimited path in the maven.eclipse.classpath.include property and creates src entries -->
<u:tokenize var="paths" delim=",">$
<j:forEach var="entries" items="$
<maven:makeRelativePath var="extraSrcDir" basedir="$
<classpathentry kind="src" path="$
This uses the comma delimited values in the property and creates the appropriate src entries.
However, i noticed that the direction of the slashes is incorrect in relation to how eclipse does it. If you update your classpath entries through eclipse, eclipse creates this:
src/java (for example)
With this "patch" and the current output of the other template statements, this path is actualy:
Eclipse doesn't complain about this, and i'm assuming this is the case because I am using windows.