Numerical computation of gas turbine flowfields demands high computing power. In the present work, we present a detailed analysis of 3D computations for a highly loaded transonic blade and for a gas turbine stage. Comparison between experimental results and numerical computations reveals the precision limits of current modeling assumptions. Computations are performed using a time-marching approach coupled with a mixing-plane model for the exchange of flowfields between stator and rotor domains. Eddy viscosity turbulence models are applied to compute the flow with and without wall functions. Limitations in performance assessment are presented regarding the level of detail used for the geometry definition, the mixing-plane approach, and the near wall turbulence model employed.