When it comes to video, especially when I'm just viewing it on my computer, I just want the stuff to play. It happened to me on Windows and it's now happened to me on my Mac - someone sends me a media format and QuickTime can't play it. I don't know why, nor do I really care all that much. Sure, I'll change my tune at some point when I start getting into video editing on my Mac but that's tomorrow's challenge. Right now what I need is something that let's me play any of the files that people throw at me. Period.
With that simple requirement on my mind and a MOV file that I couldn't watch I looked around for a cheap (free) way to view different video formats on my machine. I found VLC pretty quickly.
Suffice it to say, VLC worked great for me. I threw a couple of different files at it and it played them great. The list of file formats that VLC supports is quite long and hit all of the types I had been struggling with.