I created an eclipse project using maven, which links in the dependencies via the maven repo. It references the maven repo via the "M2_REPO" variable. When this variable wasn't set, I was unable to set the source and target java classes for the source and target models - just came back with an error ... "unable to load class ''" (i.e. empty quoted string). The classes I was trying to set were in the actual project source (i.e. not in any of the linked in dependecies), so I'm not sure what the issue was.

Might be a good thing to add this in a FAQ or Known Issues doc, or even as a "possible cause" message addition to the "unable to load class..." error message.