Got it working on my Fire Stick and Nexus 5 running on custom kitkat rom. Had no luck on the first few try, my phone can see my fire stick and when it said it's connecting, the fire tv stick also said it's "preparing" to connect to my android device with my device name on the screen, but it would just disconnect without doing anything and go back to the setting screen after a few seconds.
Then i tried to turn off and turn on my wifi on my phone, tried again, fire tv now put the tv screen into a black & blank screen, but nothing more, it would disconnect again after a few seconds later. Tried a few times later on, same result, and no luck.
Again, i turn off my wifi on my phone and tried again and it now connected wonderfully! Tried youtube video on my phone and it's watchable on the tv, i'm going to try out a local video tomorrow and see how does it perform, so far i'm happy with browsing my photo in my phone alone without lags i found unacceptable on chromecast (but to be fair, it's not build for direct mirroring a device)
I have no luck in setting it up with my win 8.1 DELL e6540 laptop yet, i'm not sure if it even support miracast, would look into that also tomorrow. Right now i'm just happy it works on my phone and the quality is definitely acceptable.
Hope it helps someone to setup your miracast!