Altdo Apple TV Video Converter is a commercial video converter. With it, you can convert your video files into formats that can be played by the Apple TV 1 and 2. The application only accepts a handful of formats: 3GP, AVI, ASF, MOV, WMV, MP4, M4V and MPEG. MKV is not supported and that is the format that I convert the most at home. The supported output formats are MPEG-4 for video and AAC and MP3 for audio. There is only one conversion profile for the Apple TV, and you can only customize the quality (low, normal, superb, and retain original data).
In terms of design, this application leaves a bit to be desired in my honest opinion. It looks plain old. The graphical user interface isn't elaborate at all. In terms of performance, I can say that the converter does an OK job. I tested this by converting an AVI file to the "superb quality" setting. The file looked good, but its aspect ratio was changed to 4:3, which distorted the image.
In short, for $29.95, you can get lots of better converters out there, and there are free alternatives better than this as well.