I'm a developer of a Linux video editing software, and I use OpenGL for playback and compositing of Videos.
It would really be interesting to include some tests into the benchmark suite that drive the features of 3D-Hardware that is required for Video Textures to the Limit, and to see how different Hardware/Drivers compare in those respects.
It's especially interesting, because I already noticed some problems with ATI hardware(or drivers?) for features that would be really important for this stuff.
There are two interesting projects on sourceforge that could be used as testing tools:
The Video Player available from the following Project is similar, although a little simpler, but IMHO the sourcecode is easier to understand, and could be used for a custom Benchmarking tool. http://sourceforge.net/projects/yuvtools
btw. this is probably more interesting for video production, and not so much for simple playback.
Especially now that HD camcorders are more popular, Video Editing and Compositing is better and faster on the 3D-Hardware than when only using the CPU.