It is extremely challenging to run controlled studies comparing multiple Augmented Reality (AR) systems. We use an AR simulation approach, in which a Virtual Reality (VR) system is used to simulate multiple AR systems. To investigate the validity of this approach, in our first experiment we carefully replicated a well-known study by Ellis et al. using our simulator, obtaining comparable results. We include a discussion on general issues we encountered with replicating a prior study. In our second experiment further exploring the validity of AR simulation, we investigated the effects of simulator latency on the results from experiments conducted in an AR simulator. We found simulator latency to have a significant effect on 3D tracing, however there was no interaction between simulator latency and artificial latency. Based on the results from these two experiments, we conclude that simulator latency is not inconsequential in determining task performance. Simulating visual registration is not sufficient to simulate the overall perception of registration errors in an AR system. We also need to keep simulator latency at a minimum. We discuss the impact of these results on the use of the AR simulation approach.