When I am on a highway I leave cruise control on at all times, even in hilly country & I don't find it dangerous at all. You just have to understand how it works & that the transmission will kick back the required number of gears to maintain a given speed. The only exception to this would be for advisory speed signs that indicate a certain corner couldn't be negotiated at the posted speed limit. eg - a posted 60kph corner can be taken at 100kph, but a slower indicated corner you have to adjust your speed accordingly & this would be the only time I turn cruise control off.

