Disagree. First, the hypothesis that the quality distribution within the 2000 is substantially better than within the half-million-or-so is unlikely to be true,

Disagree. First, the hypothesis that the quality distribution within the 2000 is substantially better than within the half-million-or-so is unlikely to be true, at least there's no evidence why it should be so. Second, the 2000 is absolutely certain not to cover the long tail. The 2 dozen applications you use are not the half a dozen applications I use. Those car engine bluetooth+OBD monitors and bike repair apps are definitely not in the 2000 pool. Not to mention the variety of games out there. 2000 is a really crappy number of apps to have.