I also have a Samsung AllShare Cast Dongle for my Samsung S3. Is also Miracast, is of the Samsung marketing types but not called so and has now been renamed from AllShare Cast-in "Screen Mirroring". The actually worked OK, but is much slower in the "boot" as this stick. Unfortunately, I could barely use because Samsung has messed up by a irreverisblen firmware patch the HDMI / HDCP-recognition and the dongle by suddenly no longer to A / V receivers, some projectors or my Atrix Lapdock (a special case; long story) ran ; So all HDMI Devices, the exotic resolutions have (= not full HD) and / or do not report immediately HDCP compliance (on TV, he goes) ... has upset me very Samsung. We also now have a grade-3 "like" China-Android phone, which brings the officially supported by Android 4.2 Miracast and in the Settings "Wireless transmission" offering. It has been for a few seconds each can even connect to the Samsung dongle, the connection was then but (probably for the above reasons) stopped by the dongle.
Therefore I have given this a chance and stick it works pleasantly well: All the "exotic" HDMI devices are supported and of course TVs. Connection to S3 is stable and of the same quality as the Samsung dongle. The clone cell phone is also supported - All thing with niederiger dissolved screen content - but that is not for the sticks but the Clones or WiFi Direct bandwidth. Even with "Screen Mirroring" at the same time I could easily stream video via WiFi. Games / quick screen change laggen more times or disintegrate in Blöckchenartefakte occasionally - just like in the other Miracast solution (in principle is not really recommended).
The drive can be powered via the USB port of my TV, and from the USB ports of Lapdocks with current (important to me) - but is actually quite hot in use. That can not be good for life - I prefer from a half star. In addition, the WiFi performance of the stick is rather not outstanding and a bit more susceptible to interference, I had him bring out behind the TV and still maintain a certain distance from the router (Fritzbox) via HDMI extension cable so that the wifi direct connection between stick and mobile and WiFi Internet connection dzwischen mobile and router do not influence. That was when Samsung dongle not necessary ... Still a half star deduction, which is however almost outweighed by the significantly niederigeren price. So to repeat: I am quite happy with the stick as Miracast solution for androids.