Arnon is here at the PyCon 2015 sprints, so bringing the current status up to date:

= Why *.hex()? =

* That's the name in PEP 358
* That's the name of the comparable float method

= Why add it to the builtin types? =

* To provide One Obvious Way To Do It, rather than the current 5 (or so) non-obvious ways listed above
* That's what PEP 358 proposed

= Why postpone configurability and str.format() integration? =

* Because these are more complex questions that can be left out of the "minimum useful feature" of new methods on the builtins and hence have been moved out to issue 22385 (which depends on this issue, and would likely require a PEP to resolve all the technical details)