Lessons Learned from Planck

Planck's measurements of the microwave sky at seven frequencies spanning 30 to 353 GHz represent an important advance in our understanding of both the cosmic microwave background (CMB) radiation and the properties of astrophysical foregrounds. I will discuss the lessons learned from Planck for future experiments, particularly in the areas of foreground confusion and systematic errors that will set the ultimate limits to what can learned from CMB polarization.