  We study the implication of the time-dependent CP asymmetry in
$B\to\pi^+\pi^-$ decays on the extraction of weak phases taking into account
the precise measurement of $\sin 2\beta$, obtained from the ``gold-plated''mode
$B\to J/\psi K_S$. Predictions and uncertainties for the hadronic parameters
are investigated in QCD factorization. Furthermore, independent theoretical and
experimental tests of the factorization framework are briefly discussed.
Finally, a model-independent bound on the unitarity triangle from CP violation
in $B\to\pi^+\pi^-$ and $B\to J/\psi K_S$ is derived.
