I have an AppleTV I'm very happy with when it comes to Netflix and so but I bought a NTV300SL yesterday, primarily for the WiDi and the USB playback, both missing from the ATV3.
I'm still in the middle of testing it, setting it up was very easy (except from the WiDi but on the windows 8 laptop end, nothing to do with the NTV300SL).
First off, regarding issues with the DTS audio on MKV files, at first I thought I had the same problem but in switching the audio in the setup to "Bitstream HD" instead of "PCM Stereo" it is working great now. I can't tell if it does because I have a good receiver, or if it would work on the TV directly, so you will have to try it yourself ;-)
However, if you have an MKV movie with more than one audio track, say the primary language is Spanish and the original version, say English, in track number 2, it will play the movie in Spanish only. I haven't found any other way than recoding the file in order for it to play the original version
Please let me know if you found a way around it.
For the rest, except from the remote that could be better, I don't have any other complain so far (might be because I am not using it for Netflix based on some of the reviews I read).
So far, I must say that for this price it is doing fairly good!