As one of my image processing software (mainly based on NumPy, SciPy, guidata and guiqwt) is being limited by the "2GB per application" memory limit due to the fact that I'm using a 32bit build of Python on Windows, I'm currently thinking of switching to Python 64bit. That's why I've been recently investigating the 64bit/Windows/Python ecosystem.
1. The NumPy/SciPy building issue on Windows 64bit.
According to experienced developers, there is no decent open-source (free) Fortran compiler for the Windows 64bit platform. As a consequence, it's impossible to build NumPy or SciPy on this platform using only free and open-source tools. That's why there is no official Windows 64bit binaries for these two libraries. The only ready-to-use installers available out there were prepared by Christoph Gohlke (using Intel Fortran compiler, a.k.a. 'ifort') and these are clearly unofficial binaries. Furthermore, Christoph has built two different installers for NumPy: one unoptimized and one optimized with the Intel Math Kernel Library (MKL), hence providing better performance. And Gohlke's SciPy 64bit binary package (the only one available freely online) require NumPy MKL...
Spyder is a free open-source development environment for the Python programming language providing MATLAB-like features in a simple and light-weighted software, available for all major platforms (Windows, Linux, MacOS X).