ag4ever — I believe you! My comment was strictly about reletively flat terrain, where the cruise control behaves well, and maintains the desired speed well. On rolling hills, however, I find the cruise control's behavior really egregious. The car gains some speed above the set speed on the downhill sections (as expected, but this can be as much as 10 km/h over), but then the controller waits too long (a few seconds too long) when the uphill section begins. The speed drops significantly below the set speed (as much as 15 km/h under). Then it seems to "floor the accelerator" in order to catch up. The car then overshoots the set speed significantly, before finally settling down at the set speed. And this cycle repeats itself on each rolling hill! I've repeatedly found this in my travels. It seems to me that the feedback controller design is dreadfully suboptimal. Perhaps the long delay has to do with the signalling of the car's speed, etc., information to the cruise control ECU on the CAN bus. But the CAN is a speedy bus! Extra delay in the controller loop makes for potential instability, and this behavior verges on instability — the closed-loop system is very underdamped, and close to oscillating. I'm hoping that Toyota has a code update for this when the first firmware revision is released. Has anyone heard about such a release?

Stan