Have you considered pyscripter - An open-source Python Integrated Development Environment (IDE) ?
If yes, are you aware of any advantages of Python Win over PyScripter?
I found PyScripter better in every regard and everyone I recommend PyScripter to then always prefer it to Python Win.
Since this ancient thread was revived, for anyone interested the PyWin32 extension to use with ArcGIS 10.1 and 10.2 is Mark Hammond's Python for Windows 32-bit available on SourceForge at build 219 for Python 2.7 from the linked URL.
Allow the download to complete and then run the installer. But, you may have to make PATH and *.pth adjustments for it to function with ArcPy.
This (pyscripter) sounds pretty cool, but notice that support for Python 2.7), the version of python used in ArcGIS for Desktop 10.1+, isn't specified (FAQ - pyscripter - An open-source Python Integrated Development Environment (IDE) - Google Project H...).
I have no doubt that it will work "good enough", but it is just one more hurdle in a enterprise when there are already enough of those "trust me"s out there that I have already committed myself to w.r.t. the rest of the software/applications/data/services and their life cycles.