  Kamenev and Mezard, and Yurkevich and Lerner, have recently shown how to
reproduce the large-frequency asymptotics of the energy level correlations for
disordered electron systems, by doing perturbation theory around the saddles of
the compact nonlinear sigma model derived from fermionic replicas. We present a
critical review of their procedure and argue that its validity is limited to
the perturbative regime of large frequency. The miraculous exactness of the
saddle-point answer for beta = 2 (unitary symmetry) in the universal limit, is
shown to be a special feature due to the Duistermaat-Heckman theorem.
