The Adaptive Optics for the Telescopio Nazionale Galileo module (namely AdOpt@TNG) implements the pyramid wavefront sensor as a unique feature. This allows to get valuable information on its performance on the sky. An updated overview of the results obtained
so far is shown, including a discussion on the sources of errors in the closed loop operation, distinguishing them between the ones specific of the pyramid wavefront sensor and the one more related to the system as a whole. This system allows also for a number of experiments and check of the sensitivity of such a wavefront sensor, especially in comparison with other types of sensing units. The ways to accomplish such an experiment in a convincing way are shown along with the first results obtained so far. Finally, we describe how and up to which extent a number of practical problems encountered in the near past can be solved implementing the recent new ideas on the pyramid theme, many of which popped up from our "lessons learned".© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.