There has not been much progress for me in the past four months. As my "new" ideas no longer made noticeable contribution to the final result, I stopped working on improvements, instead, tried to develop some theory about the methods in the Netflix competition. It really bugs me to fiddle with hundreds of predictors and billions of parameters, without understanding exactly what I am doing and why.
It surely is more enjoyable thinking than computing the unchanging RMSEs. And I thought I could do that for a long time, anyway, the 10% seemed residing in a distant future. It's kinda funny in retrospect, because part of my theory was to measure the signal-to-noise ratio, thinking it might show that the data is simply too noisy to achieve 10% improvement. The team "BellKor's Pragmatic Chaos" just proved how wrong I was. It's like watching a marathon runner finished the race with a 15-meter triple jump. Amazing! Kudos to them!
It will be interesting to watch what happens in the next 30 days.