First, how is average utilitarian defined in a non-circular way?
If you can quantify a proto-utility across some set of moral patients (i.e. some thing that is measurable for each thing/person we care about), then you can then call your utility the average of proto-utility over moral patients. For example, you could define your set of moral patients to be the set of humans, and each human's proto-utility to be the amount of money they have, then average by summing the money and dividing by the number of humans.
I don't necessarily endorse that approach, of course.
Has he been officially "impressed" yet?
I think Eliezer says he's still confused about anthropics.
What reading can I do on anthropics to get an idea of the major ideas in the field?
So far as I know, Nick Bostrom's book is the orthodox foremost work in the field. You can read it immediately for free here. Personally, I would guess that absorbing UDT and updateless thinking is the best marginal thing you can do to make progress on anthropics, but that's probably not even a majority opinion on LW, let alone among anthropics scholars.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
Notes for future OT posters:
1. Please add the 'open_thread' tag.
2. Check if there is an active Open Thread before posting a new one. (Immediately before; refresh the list-of-threads page before posting.)
3. Open Threads should be posted in Discussion, and not Main.
4. Open Threads should start on Monday, and end on Sunday.