  Our presentation centers on the consequences of s-channel unitarity,
manifested by soft re-scatterings of the spectator partons in a high energy
diffractive process, focusing on the calculations of gap survival
probabilities. Our emphasis is on recent estimates relevant to exclusive
diffractive Higgs production at the LHC. To this end, we critically re-examine
the comparison of the theoretical estimates of large rapidity gap hard di-jets
with the measured data, and remark on the difficulties in the interpretation of
HERA hard di-jet photoproduction.
