We review recent results of point-contact spectroscopy (PCS) in doped (with Al, C or Mn) and neutron-irradiated samples of the two-band superconductor MgB2. The aim of these measurements was to clarify the role of inter- and intra-band scattering, and to test the theoretical expectations about the effects of substitutions and disorder on two-band superconductivity. The gap amplitudes, Δπ and Δσ, were obtained as a function of the critical temperature of the junctions (or of the doping content) by fitting the conductance curves with the two-band BTK model. The analysis of the resulting curves within the Eliashberg theory allowed us to extract information on the partial DOSs, as well as on the scattering rates within and between the two bands. The results are discussed and compared to theoretical expectations.