Disclosure: I'm one of the developers behind The Masterplan
We've been very happy with Haxe and OpenFL, but for us the most important thing is definitely not the Flash API but a cross platform way for writing games that use OpenGL ES 2.0 for rendering and OpenAL for audio. See Lime (https://github.com/openfl/lime).
We've made a tactical team-based heisting simulator called The Masterplan with this setup. It's finally coming out of Early Access today! The current release runs on Windows, Mac and Linux and hopefully we can release this on many more platforms in the future.