Now, another factor to consider is that Windows 7 makes manipulating the system PATH even more difficult to do correctly (e.g. see http://www.symantec.com/connect/forums/wise-7-win-7-problems-updating-environment-variable-current-user).

I believe ActiveState handle this by making the PATH modification optional and having it off by default (I found docs for ActivePerl stating this explicitly, but no equivalent for ActivePython).

Regardless, for a product intended for heavy command line use, we should definitely do better in either providing a way for users to request that the installer modify PATH directly, or else a way to easily launch a command shell with PATH updated appropriately.