||Results of independent mode models of molecular vibrations of SO2 and H2O are compared to converged eigenvalues and eigenfunctions. Energies of self-consistent-held and adiabatic wave functions are calculated and compared to the eigenvalues; Brueckner functions and natural medals are compared to the eigenfunctions. These comparisons are made for a class of normal coordinates of varying curvature. Of the coordinates we considered, an independent mode model based on rectilinear normal coordinates provides the best description of the energetics yet provides the poorest description of the eigenfunctions. The ramifications of this finding are discussed for both independent mode models and perturbative descriptions of molecular vibrations.