Spinning reserves are an electricity grid operator's first strategy for maintaining system reliability following a major disturbance. The Demand Response Spinning Reserve project has demonstrated that it is technologically feasible to provide spinning reserves using aggregations of small, controllable residential appliances. This paper addresses two concerns stemming from the high cost of real-time telemetry, which makes it impractical to monitor individual, small appliances comprising an aggregated demand-response resource. First, time-stamped information taken at each stage in a load curtailment sequence, starting with the grid operator's initial dispatch command and ending with the receipt of the command by the residential appliances, is analyzed to measure the speed of demand response. Second, load information from distribution feeders serving aggregations of controlled appliances along with end-use monitoring information collected from a sample of the appliances are analyzed to estimate and understand the influencing the magnitude and statistical significance of the amount of load curtailed.