Much recent work has focused on improving AQM performance through expediting response time. In this paper we explore the impact of propagation delay and topology on AQM, discuss the question "faster the AQM controller responds, better it is?" We show that sometimes the fast responsive AQM controller leads to reduced link utilization and higher queue oscillations. Using simulations, we conclude that the performance of AQM is related to the network topology, propagation delay and the AQM schemes adopted by contemporaneous routers. Conservative scheme, such as PI, will be reassuring in uncertain network environment.