Although supremely unhospitable to life today, Venus's geodynamic similarities to Earth provide the ultimate control case for understanding rocky planet evolution and habitability. It very likely had past long-term surface water, as well as a dynamo. Tectonism and volcanism, with associated outgassing, likely persist today. A majority of rocky Earth-sized exoplanets lie in the high insolation "Venus-zone". The ultimate question is are any of them habitable?