With the new GObject-Introspection 1.40, gir generation now works with MinGW-W64 CRT and most docstrings issues seems been squashed too. GTK is not on Windows side though, version 3.12.1 looks buggier where an app (in this case gtk3-demo) will lose toplevel window (the one that is native and directed by OS), wish I have screenshot to show (I will). All 3.10 bugs also persist in 3.12, so despite of lots of new features it's really no good at the moment.
GTK 3.12.1 has lots of fixes in the Win32 theme (FYI, it's controlled by compiled-in css files namely gtk-win32*.css) which I tried to backport to 3.8.9 and 3.10.8 with some success, I also made correction on Windows XP specific part. But realized that perfect "theming emulation" is not possible yet with current css feature and event handling.
Overall there are new lots of libraries joined the AIO packages, with over 100 introspected libraries. The 64 bit port is not convincing... In some of my tests GI fail to resolve to existed exported functions of a dll, possibly getting skipped/mangled in the process. At C level, the libraries/apps behave just as good as 32 bit ones, so the problem is pygobject specific here.
Download for Python 32bit at: