As a full time Arch user the change was a little annoying at first but now I am perfectly happy using Python3 as the default because all my Python shell scripts and system installed packages work under Python3. I can simply work in a Python2 virtualenv when I need python2.
As of version 1.7 (2011), --no-site-packages is default behavior.
I still specify it every time anyway, but thought it'd be worth mentioning. :)
The --python switch is really great, though, particularly now that 3 is getting distro traction and most of us who work in Python are likely maintaining a lot of 2.x projects. Thanks!