Newcomb's problem is important because it led (may be not directly, but I think it contributed) to the schism into evidential decision theory and causal decision theory.
As far as I can tell, that's because the causal decision theorists are crippled by using magicless thinking in a magical problem. The only outcome is "huh, people who use all the information provided by a problem do better than people who ignore some of the information!" As schisms go, that seems pretty tame.
The issue is expressing formally the algorithm which uses all the information to get the right answer in Newcomb's.
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?)