Interactive computing systems frequently use pointing as an input modality, while also supporting other forms of input. We focus on pointing and investigate the effects of variations, i.e. jitter, in the input device latency, as well as dropouts, on 2D pointing speed and accuracy. First, we characterize the latency, latency jitter, and dropouts in several common input technologies. Then we present an experiment, where we systematically explore combinations of dropouts, latency, and latency jitter on a desktop mouse. The results indicate that latency and dropouts have a strong effect on human performance; moderate amounts of jitter in latency do not change performance in a significant way in most cases.