  We review the progress in the QCD calculation of inclusive decay spectra. It
was recently shown that the inherent infrared finiteness of inclusive spectra
extends beyond the level of logarithms. Dressed Gluon Exponentiation makes
practical use of this property by computing the Sudakov exponent as a Borel
sum. Based on renormalon analysis, infrared sensitivity in the exponent is
reflected in power corrections that are inversely proportional to the third
power of the mass. Therefore, the parametric enhancement of non-perturbative
corrections near the phase--space boundary is effective only in a small region.
Consequently, the on-shell decay spectrum provides a good approximation to the
meson decay. In particular, it facilitates a precise determination of V_ub from
present measurements of inclusive charmless semileptonic widths without
involving a non-perturbative ``shape function''.
