It's open source (GPL2) and totally free.

Keybindings and other options can be changed in the respective configuration files, and a plugin interface allows for extending with more features.

Everything MPV needs to play media files is contained within which means no outside codecs are needed.

The whole interface is just a video with a minimal OSD.

Very responsive seeking even on high bitrate video.

Always up to date, rapid development.

When used with youtube-dl.

Intelligently caches livestreams and enables jumping within the cached stream.

MPV leverages the FFmpeg hwaccel APIs to support VDPAU, VAAPI, DXVA2, VDA and VideoToolbox video decoding acceleration.