  We present a new QCD sum rule with high sensitivity to the continuum regions
of charm and bottom quark pair production. Combining this sum rule with
existing ones yields very stable results for the msbar quark masses, m_c(m_c)$
and m_b (m_b). Comparison of our approach with experimental data allows for a
robust theoretical error estimate. We have also provided a new evaluation of
the lifetime of the tau lepton, serving as a strong constraint on alpha_s.
