Since the discovery of a high piezoelectric response in AlScN by Akiyama and coworkers in 2009, a number of works of other groups confirmed the large increase of piezoelectricity when partially substituting Al cations by Sc cations, as long as the alloy grows in the wurtzite phase. This contribution will present an overview of current knowledge, and compare property data from different authors, including also properties obtained from first principles. It will comment on the values of the effective thin film piezoelectric coefficients e(31),(f) and d(31),(f).