Works, But slow
Ive been using Turbo.264 HD Video Converter to convert MKV video files to 1080p Quicktime files. Turbo works fine on 95% of my files but some it just wont do. It is very easy to use, but it is also slow, taking 4-5 hours to convert a 2 hour 1080p MKV file on a 2011 MacMini with 8GB of Ram and a solid state drive. My recommendation is to purchase Elgatos hardware converter by the same name, the Turbo.264 HD which has a usb hardware decoder as well as the software sold here for $99 direct from elgato. Files convert 3X faster and it comes with the same excellent software.
scubag about Turbo.264 HD Video Converter