The E5151 has lots of settings available, like any good router.
One feature I must mention is quick boot. It's supposed to start up in 5 seconds, and it really works! Sometimes it takes longer, but it still booted up in around 10 seconds.
To save power, it only connects to 3G as needed, like a phone. It will also let its WiFi sleep if it's not been used for a certain amount of time. I think this can be disabled. When sleeping, clicking the Power button will wake it up.