The Mqtt binding works actually. Open issues are mostly enhancement requests if you see the Homeassistent part as still being in beta.
Unfortunately I lost the Mqtt Homeassistent contributor due to the buildsystem change.
The underlying paho library with its really sad state atm causes problems for script users though. I’m thinking of changing the library after OH2.5 has been released.
Hue emulation also works, but expects json type http posts. Alexa has a defect thought and is sending json with the mimetype plain. There is a fix pending on hueemulation to act more relaxed.