  We describe some of the recent progress in the calculation of thermodynamic
quantities in QCD at high temperatures and densities by weak-coupling
techniques and extrapolation to realistic coupling strength. We argue that a
(mostly) weakly coupled quark-gluon plasma at temperatures only a few times the
transition temperature is not yet ruled out by the observed fast apparent
thermalization at RHIC, as nonabelian plasma instabilities might provide an
efficient mechanism for fast isotropization even in a collisionless plasma.
