Doremisoft Mac MKV Video Converter is a commercial video converter. Just disregard the MKV on its title, though, since this is more of a standard video converter. In other words, it simply doesn't come with any features that are relevant for MKV conversion. But I will get to that in a second.
Graphically, this converter looks like any other converter by Doremisoft. It has a very nice interface. I like the color choice (black, blue and gray). There is a space for your conversion queue and a video player to watch your videos before conversion. At the bottom of the screen you will find the conversion profiles. There are quite a few: for devices that range from iPods and iPhones to Blackberry and Gphones. You can also not choose a profile and select the output format directly. The app can convert files into MKV, MP4, MOV, DV, AVI, and an array of other formats. The input format support is also very good.
This converter comes with a video editor built in that allows you to crop your videos, and to adjust their brightness, contrast and saturation.
As I mentioned above, this converter doesn't really have any features that you would want in an MKV converter. There is no support for subtitles, no GPU acceleration, and you can't add multiple audio tracks to your files.
In my testing, the application performed well. I converted an HD MP4 file into MKV with no problems. The resulting file played great on VLC.