  We analyse here the role electrons on Anderson-U impurities play in
superconductivity in a metal alloy. We find that phonon coupling at impurities
counteracts the traditional effects which dominate T_c suppression in the
non-magnetic limit. In some cases, we findt hat non-magnetic impurities can
enhance T_c. In the Kondo limit, a Fermi liquid analysis reveals that it is the
enhancement in the density of states arising from the Kondo resonancethat
counteracts pair-weakening.
