It can play just about anything without needing to convert it first. It is fast and efficient and can even re-encode video files into a myriad of different formats (great for quick format changes). It can also screen record your screen and record from an external device such as a camera or capture device. And it's networking tools, though I'm not an expert, are pretty powerful.
It is Open Source (meaning its free forever) which means it has a ton of extra plugins, support forums, and customization opportunities.
Though I've never used it for this, I've seen and been told that is can be used as a media library organizer as well (like an iTunes replacement).
Deployable (or portable) versions have been allowing the program to run on external drives like USB drives and CDs.
Not really much else to say, it really does what it says on their website and does it well, for the most part.
It needs some extra functionality, better interface, and fewer bugs. It still can't play some video files, nor can it play swf files, which I would really, really like.
It also is kind of intimidating to new users as it has no "introduction" screen or anything like that (not that it needs that though).
It allows us to play, record, and preview older video file formats that we get from clients without cost or struggle.