There are a number of performance limiting factors that concern the designers of machine tool servo systems. One such factor is the mismatch that often exists between motor and load inertias. This paper briefly discusses the results of a previous study on the factors that interact to introduce stability problems in the presence of a high motor-load inertia mismatch. The effects of such an inertia mismatch, on servo system performance, are then discussed and analysed using closed loop frequency responses. Various methods of improving the system response using fast feedback control are presented, including traditional PI control and modern methods incorporating full order state observation. The effectiveness of these control methods are then compared after comprehensive testing on a specially constructed experimental rig.