I've found that for Maven based projects, there's a fast way of doing this which doesn't require any plugins or fuss:
$ mvn eclipse:eclipse -DdownloadSources -DdownloadJavadocs
Why not m2e?
I've never had much luck with m2e, it just doesn't like me. So, I
stick with using
mvn eclipse:eclipse and restarting/refreshing
the Eclipse project whenever something major changes. It works.