I'm in favour of adding /Library/Python/x.y/ to sys.path for Python 2.7 
and 3.1 and will work on that during the Pycon sprints.

/Library/Python will be added after the site-packages directory inside 
the framework instead of replacing the latter directory. The reason for 
this is that we don't want to install all packages in a location that's 
visible to Apple's copy of Python because you could accidently replace 
packages that Apple ships as part of the "Extras" directory that way. 
Replacing those is bad because those libraries are used by Apple system 
software and replacing stuff might therefore break the system 
(particularly on server systems).

I won't backport to 2.6 and 3.0 because this is a feature request and 
not a bugfix.

W.r.t. building PIL and other extensions: we've had a discussion about 
this during the startup phase of the macpython-sig sprint and we have 
some ideas to make this situation less painful in the future (without 
necessarily having to patch Python for that).