It is helpful, and was one of the ways that helped me to understand One-boxing on a gut level.

And yet, when the problem space seems harder, when "optimal" becomes uncomputable and wrapped up in the fact that I can't fully introspect, playing certain games doesn't feel like designing a mind. Although, this is probably just due to the fact that games have time limits, while mind-design is unconstrained. If I had an eternity to play any given game, I would spend a lot of time introspecting, changing my mind into the sort that could play iterations of the game in smaller time chunks. Although there would still always be a part of my brain (that part created in motion) that I can't change. And I would still use that part to play the black box game.

In regards to metaprobabilities, I'm starting to see the point. I don't think it alters any theory about how probablity "works," but its intuitive value could be evidence that optimal AIs might be able to more efficiently emulate perfect decision theory with CalcMetaProbability implemented. And it's certainly useful to many here.