Using the recently developed Car-Parrinello-like approach to Born-Oppenheimer molecular dynamics ( Kühne, T. D. ; et al. Phys. Rev. Lett. 2007 , 98 , 066401. ), we assess the accuracy of ab initio molecular dynamics at the semilocal density functional level of theory to describe structural and dynamic properties of liquid water at ambient conditions. We have performed a series of large-scale simulations using a number of parameter-free exchange and correlation functionals, to minimize and investigate the influence of finite size effects as well as statistical errors. We find that finite size effects in structural properties are rather small and, given an extensive sampling, reproducible. On the other hand, the influence of finite size effects on dynamical properties are much larger than generally appreciated. So much so that the infinite size limit is practically out of reach. However, using a finite size scaling procedure, thanks to the greater effectiveness of our new method we can estimate both the thermodynamic value of the diffusion coefficient and the shear viscosity. The hydrogen bond network structure and its kinetics are consistent with the conventional view of tetrahedrally coordinated water.