4Videosoft FLV Converter for Mac is a commercial video converter. When I downloaded this converter, I was expecting it to be a very-limited converter. After all, most "FLV" converters only let you convert FLV files into a few other formats. Don't ask me why, but this application doesn't restrict the formats that you can open with it. I tried opening MKV, AVI, and H.264 files and they were all loaded successfully. Also, the output format support isn't bad at all. There are tens of formats supported, and a lot of conversion profiles. Devices like the iPhone, iPad, iPod Touch, Xbox 360, Playstation 3, Wii, and various mobile phones are all supported.
Graphically, this converter looks like any other converter by 4Videosoft. The GUI is simple and intuitive. There is a video player on the right, and the conversion settings at the bottom of the screen. A video editor lets you trim and crop your videos and adjust some of their properties, like brightness and contrast.
In terms of performance, 4Videosoft FLV Converter for Mac does not disappoint. I tested it by converting an FLV file into MPEG-4, but I also was able to convert an HD MKV file into an HD MOV one.