Not sure if the Windows version of Ruby Qt 4 bindings has been released
yet. The project page is
http://rubyforge.org/projects/korundum/ and
Richard Dale is the man in terms of knowing the latest info. The last I
had heard the Ruby Qt 4 bindings were Linux only, as the development
team didn't have ready access to a Windows environment to port things
over to.
As for experience, I have used an earlier version of Ruby Qt bindings
based on Qt 2. This version I used on Windows for a GUI app project,
but didn't have the compilation environment to build it from source. So
I reverted back to an older version of Ruby (1.6), which had binary
files for the Qt 2 bindings that I could download.
This same GUI app project I then ported over to ARM Linux (specifically
a Sharp Zaurus SL-5500), using Ruby Qte bindings I found on
https://sourceforge.jp/projects/zaurus-ja/. The tricky thing was that
to pull off the port of this project the ARM Linux version was using
Ruby 1.8, although at least it was still binding to a Qte environment
based on Qt 2.
If Qt 4 bindings aren't available yet for Ruby on Windows you might
have to revert back to Qt 3, which appears to be an option for your
situation. Would this suffice, or is there something specific in terms
of methods, objects, etc. in Qt 4 that is missing from Qt 3 that your
work requires?