Just a few thoughts from someone who uses Windows and who'd need to change code for this change:

1) I don't know if waiting to 3.5 is needed.  I can make the change to look in the bin directory fairly quickly.

2) Is it safe to add scripts to the PATH?  I'd worry about something in there that's named so it clashes with a standard program such as notepad or chkdsk or more likely something else from another 3rd party program that is installed.

3) A python3.3.exe command should be added so that if someone installs both 3.3 and an eventual 3.4, he or she can run both.

4) The uninstaller should remove the PATH entry if at all possible.

Another alternative is to provide a Start menu item for a "Python 3.4 Command Prompt" that would set up the environment that's similar to the Visual Studio 2008 Command Prompt.