Here: www.nalp.org/assets/library/171_0503llm.pdf Bottom line: If you are going to do tax, it might be worthwhile. Otherwise, forget it.
I would disagree with the article. Any graduate degree is a plus over someone with just a bachelor degree. I work in aerospace where a knowledge of law is a big plus for employees involved with program management contracts, procurement, human resources, import/export, and corporate ethics. I am sure this would apply to other industries. Looks like a thesis/disertation topic here: "The usefulness of the LL.M. in the job market."