Mininet is not a simulator. As you construct larger networks and generate more and more traffic, you will find that any accurate timing measurements you attempt to make become a more accurate reflection on the capabilities of your processor rather than on the characteristics of your topology.
Having said that, mininet is very well suited to experiments that are network-limited and whose total resource requirements fit within what a single modern multi-core server can provide. Indeed there is an entire blog, Reproducing Network Research, dedicated to reproducing cutting-edge networking research on the Mininet platform. Experiments include investigations of TCP buffer and window sizing, recreations of denial of service attacks, and examinations of wireless network performance.