We discuss the consequences of the dispersion of the energy bands in t
he broken symmetry (charge- and spin-density-wave) states of highly an
isotropic metals. Such dispersion becomes important with increasing de
viations from perfect nesting, and leads to differences between the ga
ps as sampled by transport and optical measurements. We discuss the av
ailable experimental results obtained in a variety of materials with d
ifferent band-structure anisotropy.