  We reconsider the Cross and Fischer approach to spin-Peierls transitions. We
show that a soft phonon occurs only if Omega_0<2.2 T_SP. For CuGeO_3 this
condition is not fulfilled and the calculated temperature dependence of the
Peierls-active phonon modes is in excellent agreement with experiment. A
central peak of a width ~0.2 meV is predicted at T_SP. Good agreement is found
between theory and experiment for the pretransitional Peierls-fluctuations.
Finally, we consider the problem of quantum criticality in CuGeO_3.
