Via my own digging, it appears you have to be a site  collection admin
in order to create  new pages  in the default publishing  site "pages"
library. Site admin/full control  for just that site does not work.
This seems a huge security oversight on MSFT's part--I shouldn't have
to give people control over everyone's sites  in order to create
content in their own. Has anyone heard if this is a bug  with a
planned fix or anything?

And just to conclude this conversation with myself, and in case
anyone else comes across this, it appears that you have to give
people working in publishing  site pages  libraries read access  to the
site collections master page  gallery. I don't know what the default
permissions are for those galleries, or if there is any inherent risk
in giving everyone read access to them (so you don't have to manage
them on a person-by-person basis). Would love to hear people's
thoughts on the latter.

It is a permissions issue, but its not a bug. You don't need to give
them permissions over everyone's site, just certain specific lists in
the top level site  of the site collection. If I remember right off the
top of my head they need access  to the Master page  and page layouts
gallery of the top level site in the site collection, and I think all
they need is Read access to it. Full control  of a local site won't give
them that access at the root of the site collection and if I remember
right Read access in the root of the site collection doesn't give them
exactly what they need either.

I'll see if I can find some more details in my notes.