Using own ESO-MTI/FEROS observations for 31 Galactic O-type stars, we performed a detailed quantitative analysis of these stars in terms of fundamental parameters, and rotational and extra line-broadening velocities. In practice, effective temperatures and surface gravities were determined by means of the recently updated version of the FASTWIND atmosphere code, while rotational and extra line-broadening velocities were evaluated applying a newly developed Fourier-transform + goodness-of-fit technique, assuming a radial-tangential distribution of velocities for the extra broadening. By means of the resulting data and incorporation of similar data for O-stars and B-supergiants from the literature, we investigate the properties of projected rotational and extra line-broadening velocities as a function of stellar parameters and stellar evolution, trying to put constraints on model predictions for the evolution of rotational rates of hot massive stars.