Do you work with video and audio files a lot? Especially if you use a lot of open source applications to do so, you probably run into situations where you're not sure what codec you need to get a file to run or you need to know about the encoding bitrates that apply to various files. Codec incompatibility can be a big bugaboo with open source software as can getting a hold of good open source utilities that can tell you everything you need to know about rich media files. Whether you're running Windows, the Mac OS, or Linux, a good tool for solving these problems is MediaInfo.