  The main obstacle in describing inclusive decay spectra in QCD - which, in
particular, limits the precision in extrapolating the measured \bar{B} \to X(s)
gamma rate to the full phase space as well as in extracting |V_{ub}| from
inclusive measurements of charmless semileptonic decays - is their sensitivity
to the non-perturbative momentum distribution of the heavy quark in the meson.
We show that, despite this sensitivity, resummed perturbation theory has high
predictive power. Conventional Sudakov-resummed perturbation theory describing
the decay of an on-shell heavy quark yields a divergent expansion. Detailed
understanding of this divergence in terms of infrared renormalons has paved the
way for making quantitative predictions. In particular, the leading renormalon
ambiguity cancels out between the Sudakov factor and the quark pole mass. This
cancellation requires renormalon resummation but involves no non-perturbative
information. Additional effects due to the Fermi motion of the quark in the
meson can be systematically taken into account through power corrections, which
are only important near the physical endpoint. This way the moments of the
\bar{B}\to X(s) gamma spectrum with experimentally-accessible cuts - which had
been so far just parametrized - were recently computed by perturbative means.
At Moriond these predictions were confronted with new data from BaBar.
