I believe people actually use the Windows nightly binaries, but probably not much on other OS.
I'd be curious how. As mentioned in https://github.com/geany/geany/issues/1979, the current Windows nightly builds are not compatible with the usual releases since the MSYS2 switch.
@b4n is it worth the effort and worth the increased build time on Travis? This would grow the build matrix. I think having test builds against the minimum GTK versions is nice to have but probably enough once a day and not for each push.