Python as alternative to Visual Basic

[Aaron Ginn]

I'm investigating the feasibility of using Python instead of Visual 
Basic for a commercial software package that I'm planning on developing. 
  Now I'm absolutely a Python zealot.  I use it for most of my software 
development at work where I work in a Solaris environment.  To me, 
Python is the perfect language for most applications in a UNIX 
environment where a compiled language is not required.  However, I'm not 
so sure about Windows.

The software package I'm developing will make calls to Excel and Access 
and requires a very usable GUI for users who are not particularly 
computer literate.  My first question is: what is the best choice for a 
GUI toolkit on Windows?  I've used Tkinter for UNIX to some degree of 
success, but I'm not sure this is the best choice for Windows.  Second, 
if I choose to make the application cross-platform (Windows and Mac OS X 
in particular), what would be the best choice for a cross-platform GUI 
toolkit?  I was thinking of looking at PyQt.  Is there a better option?

Basically, I'm trying to make a case for Python to the other developers 
of this software package as I believe it offers numerous advantages over 
VB in terms of speed of development, a quick learning curve, and 
maintainability.  Can anyone help me make that case?

Thanks,
Aaron