It's not interesting as a brain teaser but as a test case for decision theories. Newcomb's is especially interesting because Newcomb's-winning agents have the potential to reach Pareto efficient outcomes without needing precommitments or other outside help.
I have not seen any place to discuss Eliezer Yudkowsky's new paper, titled Timeless Decision Theory, so I decided to create a discussion post. (Have I missed an already existing post or discussion?)