  We address recent momentum resolved radio frequency (RF) experiments on
ultracold trapped Fermi gases of $^{40}$K. We show that momentum resolved RF
probes provide measurements of the centrally important fermionic spectral
function. They also serve to remove ambiguity plaguing the interpretation of
momentum integrated RF experiments by establishing a clear dispersion signature
of pairing. We find that the temperature dependence of the spectral function is
dramatic at unitarity, and, importantly, smooth from above to below $T_c$
throughout BCS-BEC crossover. This should be tested experimentally, given
widespread predictions of first order behavior.
