It works, using my bog-standard 5-pin MHL cable with my HTC Butterfly today. Really nice and crisp mirroring full HD compared to mirroring 720p, as I have done with previous devices. That said, does seem to introduce problems for 1080p video playback. Videos that play smooth on the phone are a bit jittery when mirrored. Seems that rendering it at 1080p on the device as well as doing MHL output is just a little bit much (whereas the same video is smooth on other phones like the Note 2 where it is only rendering at 720p on the phone screen). The video in question has a bitrate ~10,000kbps though, it may not be a problem for lower bitrate stuff (and since exFat formatting doesn't work on the Butterfly as it does on the Note 2 I'm unlikely to watch higher bitrate videos as they will be larger than 4GB in size).