Mine has been unplugged since I got my van 4 years ago. I have the replacement sensor, but I am waiting until I replace my thermostat again so it is easy to get at. My van setup makes it tough to reach.
I did rig mine up to a switch a couple of winters ago to see if it helped with cold starts. The high idle was nice to help it warm up faster as well as give the alt a boost while idling with the front and rear blowers on high. As far as starting, I didn't notice any difference.
With a healthy GP system, batteries and starter I have not had any issues getting the van to start with temps as low as -3 to -5*F. At those temps I usually would cycle the GP's twice just for a little extra help.