Under Windows (using the MSI), 2to3.py is outdated.

http://svn.python.org/view/sandbox/trunk/2to3/ contains the working
version (rev. 66173)

Could you explain what you mean be outdated please? It looks correct to
me in the tag.
http://svn.python.org/view/python/tags/r30rc1/Tools/scripts/2to3?rev=66500&view=markup

On a fresh win32 installation (using the 3.0rc1 MSI), the C:\Python30
\Tools\Scripts\2to3.py file contents is as follows:

------------------------------------------
#!/usr/bin/env python
from lib2to3 import refactor
import sys

sys.exit(refactor.main())
------------------------------------------

This version throws an error as follows:

------------------------------------------
C:\Python30\Tools\Scripts>C:\Python30\python.exe 2to3.py
Traceback (most recent call last):
  File "2to3.py", line 5, in <module>
    sys.exit(refactor.main())
AttributeError: 'module' object has no attribute 'main'
------------------------------------------


It seems that the '.py' extendion of the 2to3 script was removed some 
time ago.

Perhaps the MSI build process uses an old version of '2to3.py' and not 
the newer version of '2to3' (without the '.py' extension) ?

It was indeed the case that I had been packaging an unversioned file. I
don't recall the details; most likely, it was a quick work-around for
2to3 not having a .py extension, yet the MSI generator only
incorporating .py files from Scripts.

I'll look into it.

This is now fixed in r66710 and r66711.