+1 on using "Program Files" by default.

In addition to the points mentioned above, there are other considerations.

In 64-bit platforms (Windows XP x64 and Vista 64-bit), programs are
segmented by their binary compatibility (C:\Program Files and C:\Program
Files (x86)).  Installing Python to the proper program directory helps
keep it organized as to it's binary compatibility.

Additionally, I often run several version of Python side-by-side, and
having these clutter my root directory is simply unacceptable.

I've been running Python from C:\Program Files for years, and I have
encountered problems, even including the recent setuptools bug, but for
the most part, these issues have been worked out.  I add C:\Program
Files\Python and c:\Program Files\Python\Scripts to my path, and things
work well.  I would think that since only a few issues remain, if Python
is moved to the standard location, any remaining issues can be ironed out.