http://i.imgur.com/tXhhMkM.jpg -- max speed recorded from a track run.
I use the 9500ix on road trips. You do have to learn how to interpret the alerts for the detector to be effective. No detector will prevent you from getting "popped". Same for laser, very quick on/off.
Around town, the gps enabled units are useful for alerting of redlight/speed cameras (both common around chicago).