Hacking on GTK-Win32 is very annoying if you have to cross compile & copy every time you make a change. It would be nice if the build system that comes out of this thread would be useful for more than just making the stock GTK packages.
I dunno, samba works pretty ok for me for development. But it's true I end up copying files a lot for testing, mainly because I teste against an installed version usually. Sometime, I use guestfish to copy the files in a windows VM snapshot (for example to test services or drivers)
Also, debugging isn't very pleasant right now for me (I copy debug files and gdb, and use gdb in windows - urgh) I haven't look at improving this side of things with gdb-server, but according to Kai Tietz, it should be fairly straightforward (and I have used gdb-server in the past, but long time ago)