  We complete the next-to-next-to-leading order QCD calculation of the
branching ratio for B -> X_s l^+ l^- including recent results for the
three-loop anomalous dimension matrix and two-loop matrix elements. These new
contributions modify the branching ratio in the low-q^2 region, BR_ll, by about
+1% and -4%, respectively. We furthermore discuss the appropriate normalization
of the electromagnetic coupling alpha and calculate the dominant higher order
electroweak effects, showing that, due to accidental cancellations, they change
BR_ll by only -1.5% if alpha(mu) is normalized at mu = O(m_b), while they shift
it by about -8.5% if one uses a high scale normalization mu = O(M_W). The
position of the zero of the forward-backward asymmetry, q_0^2, is changed by
around +2%. After introducing a few additional improvements in order to reduce
the theoretical error, we perform a comprehensive study of the uncertainty. We
obtain BR_ll(1 GeV^2 <= q^2 <= 6 GeV^2) = (1.57 +- 0.16) x 10^-6 and q_0^2 =
(3.76 +- 0.33) GeV^2 and note that the part of the uncertainty due to the
b-quark mass can be easily reduced.
