One problem is that even if I found that VP8 performed very well at one or two particular clips (out of the 28 HD test clips available), I couldn't say for sure why that is the case. There seems to be no clear information on what clips benefit from what kind of features, and as I'm not an expert on video encoding technology, it'd be hard for me to deduce these things by myself. General conclusions could still be reached, obviously, but if I was going to such lengths it'd suck if I couldn't get more overall detailed results.

Anyway, I brought up the subject to some Xiph folks over at IRC. Maybe in the future the test clips will come equipped with more detailed information to help in testing. It'd also benefit smaller scale tests, since it'd allow one to identify possible biases more easily.