iCoolsoft MP4 Converter 

iCoolsoft MP4 Converter for Mac is a commercial video converter. It can be used to convert all your video files. I don't think there are any format limitations in place for input files, and the app can output files in H.264, MPEG-4, MPEG-1, MPEG-2, ASF, MKV, MOV and more formats. So I don't really see a reason why there is an "MP4" in the application's name.

Graphically, this converter looks very good. It has a nice color scheme and an easy-to-understand design. When you load a file onto the application, it will be listed along with a snapshot of the first frame of the video. For each file, you will see the original resolution, length, and filename. On the right part of the entry for each file, you will see the format that it will be converted to and the target resolution and length.

The app comes with a video editor that allows you to trim and crop your videos and adjust some of their properties.

In my testing, I converted an MKV file into MOV. The process was fast and the resulting file looked good. I also used the trimmer, and that also worked fine as well.