[Edit: As some users are suggesting, these numbers are skewed to RT devices since it measures RT app usage via the Store. The opposing theory says that those on Windows 8 proper simply don't use RT apps as much as those with a Surface.
That is certainly plausible although without any firm numbers of usage patterns of non-RT users, it's hard to say for sure. Due to the "in your face" approach of the RT interface and Store we're not entirely convinced of the distinction just yet.]