  The triple differential spectrum in \bar{B} -> X_u l \bar{\nu} is computed by
Dressed Gluon Exponentiation (DGE). In this framework the on-shell calculation,
converted into hadronic variables, can be directly used as an approximation to
the meson decay spectrum, without involving a leading-power non-perturbative
function. Sudakov resummation for the fully differential \bar{B} -> X_u l
\bar{\nu} width is formulated in moment space, where moments are defined using
the ratio between the lightcone momentum components of the partonic jet p^+/p^-
and the hard scale is p^-. In these variables the correspondence with the
\bar{B} -> X_s \gamma case is transparent. The Sudakov exponent is known to
next-to-next-to-leading logarithmic accuracy. Further constraints are put on
its Borel sum using the cancellation of the leading renormalon ambiguity and
the absence of the next-to-leading one, which was proven in the large-beta_0
limit and assumed here to be general. Based on the resummed spectrum, matched
to the fully differential NLO result, we calculate the event fraction
associated with experimental cuts on the hadronic mass (or the small lightcone
component) as well as on the lepton energy. Finally, we extract |V_ub| from
recent measurements by Belle and analyze the theoretical uncertainty.
