The signal-quality and especially the range (about rooms away!) Is very good and in S3 at very moderate battery consumption. The dongle itself can be powered by the supplied 4.75V / 0.55A power supply or from almost any USB port via microUSB cable. I find the presentation very well; in particular, there is no overscan problems (which could also not adjust the S3) - the picture is full frame and in the proper aspect ratio for display that are not Full HD ... but as so often reported here "only "in 720p60 (holding as on the S3 display itself). That's actually a good thing, because even at this resolution you can see quite occasional mild stuttering and finely structured with rapid changes graphics weak compression artifacts. That would certainly be much more pronounced at 1080. But the tiny artifacts disturb not really - I then wanted to see them. I am also very satisfied with 720p for the simple reason, because I run an Acer Pico LED Projector, like they come from a (cheap) HDMI Adapter for the S3 did not get along with 1080p.
What is the advantage over the HDMI adapter cable solutions? Now on the one hand you can move the S3 free and control movies, etc. directly on the device, on the other hand the MHL / USB OTG port on S3 is free and you can USB sticks / hubs / keyboards / mice / Game Controllers (!) Etc Connect., and in addition to films (eg from USB stick) look & play even on large LCD displays actually work "properly". I connect a television, projector and the HDMI monitor of a "Atrix Lapdock" by the dongle with the S3 and the keyboard / mouse / USB ports are available through a USB OTG connection.
One limitation unfortunately there: One can obviously no Bluetooth audio device or normal 3.5mm Cable Earphone "connect" and parallel to the AllShare Cast Video - operate transfer (MP3 player from the home screen, etc. but goes) (!) , In the case of the cast connection is terminated with an appropriate message immediately (quite dramatic!). So video-audio-out goes only via Cast / HDMI. This is bearable, since one can normally use an A / V receiver as HDMI terminal also, for example, or can operate headphones on display.
The only real drawback (besides the relatively high price) is not 100 percent connection. Once the connection, it is stable, but if the coupling is enabled for dongle from the S3 settings, it is (too) often happens that they break off immediately. This has nothing with cables (one can any reasonable quality HDMI cable to connect) or Rooting do. I have a ungerootetes S3 with the standard Jelly Bean. If I simply neustarte the S3, the connection works immediately ... The well is then obviously more of an issue of S3 firmware as the dongle and hence there is the hope that it comes more easily in the future - until then I draw a star from because the dongle is indeed explicitly intended as S3 accessories.
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PS supplements for true geeks: While you can as I said, the audio devices (in particular headphones) do not use parallel to AllshareCast for video transmission, but via USB OTG can be easily a cheap USB sound DAC (eg "BIGtec USB sound card 7.1 USB Adapter "for single-digit euro amounts have here) connecting the S3. About one gets then the audio output of the S3 from the DAC (Cast / HDMI is then mute / video continues to run on Cast / HDMI) - but unfortunately not lip-sync. Even goes as hotplug - if you subtract it during operation, the sound comes back via Cast / HDMI. But that's really gimmick.
Another addition: the BS Player app (there is also a free version) as a video player, you can a) get the video in a pop-up window on the S3 and continue playing at the same time in full-frame on the TV and this video window is also scalable and even transparent - so you can play a video and still continuing to work / surfing etc ... b) can also be adjusted with the BS-Player audio-video delay and so the solution to the USB DAC headphones actually lip-synched to use again.
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EDIT (17/12/2012): ... and a supplement because myself was not aware of how to actually maintain the firmware of the dongle: Today came on my S3 a Play Store update message for an AllShare Cast Firmware Update app (the I had not even installed). The next time you connect to the dongle this "hidden" by the installation system app and demand will then transmit a firmware update via WiFi Direct. For me, the dongle firmware "LH29" on "LJ02" has been updated. I have the impression that it connects now faster and easier but I have to try a few more times. So do not install any apps itself, but apparently just wait.
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EDIT (30.07.2013): WARNING: who - like me - operates the dongle together with a Atrix Lapdock, should NOT update to the published today AllShare Cast firmware ME29. Although then still operate projectors and TV etc., the more exotic resolution from Lapdock but apparently no longer supported. Anyway disconnects again immediately :( Anyone has an idea how I again can "downgrade" to LJ02, may like to write something in the comments ...
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ADDITIONAL (01/26/2014):
Unfortunately, you can not downgrade the dongle firmware and Samsung is not jerks (you get text modules to answer for inquiries) ... By the introduced in ME29 strict HDCP / HDMI control of the dongle for me is unfortunately hardly still usable. Directly on the TV and one of my beamer he goes, but once the display is not (fast enough) HDCP compliance reports or an unusual resolution has, or even an A / V receiver plugged in between, nothing more. Because this is a pure software problem (with the old dongle firmware went all) and Samsung apparently has no intention, it what to do, I'll go down from 4 to 2 stars.
I have now also yet another Android 4.2 Miracast-enabled phablet. This connects even with the Samsung dongle, but is interrupted by seconds (directly on TV). I have among other things, why a "bestbeans Miracast / DLNA" dongle brought, although it provides somewhat inferior image quality. Both devices (the S3 and the phablet) can no problems with the dongle via Miracast (when Samsung so now "Screen Mirroring" called) and connect the bestbeans dongle can also be stable at all exotic displays and HDMI-capable receivers and my Atrix operate Lapdock.
So: Who wants to see only the display of his device Samsung exclusively on TV (in quite good quality) may like to purchase this ASC dongle, I can all the others be no buy recommendation.