Hadronic tau decays provide several ways to extract the
Cabbibo-Kobashi-Maskawa (CKM) matrix element V_{us}. The most precise
determination involves using inclusive tau decays and requires as input the
total branching ratio into strange final states. Recent results from
B-factories have led to a discrepancy of about 3.4 sigma from the value of
V_{us} implied by CKM unitarity and direct determination from Kaon
semi-leptonic modes. In this paper we predict the three leading strange tau
branching ratios, using dispersive parameterizations of the hadronic form
factors and taking as experimental input the measured Kaon decay rates and the
tau -> K pi nu_tau decay spectrum. We then use our results to reevaluate
V_{us}, for which we find |V_{us}|=0.2207 \pm 0.0027, in better agreement with
CKM unitarity.Comment: 20 pages, 3 figure
