Idling temp would have more to do with fan turn on temp, then the thermostat.

I know in my car, the temps will rise in heavy traffic or stopped. The great thing about the 180 stat is when I encounter these types of situations, I start out at 180 and eventually increase to 210-220. Before with the factory stat, I would be at 220 right away. Cooler anytime is better.

Just to add my two cents, my gauge varies from 175 to 200 during regular operation and up to 220 when sitting in traffic. Freaked me out the first time I looked over and saw it at 220. Thought I was going to be sitting on the side of the road with the hood up. From reviewing this thread, looks like it is a regular occurence with the 180 T-stat installed. I feel a little metter but would like to see it stay at the rated temp.