I
Lotus7 with the best of 'em, but to try and answer the OP's question: I use cruise control daily, and see no reason to disable it when going up or down hills - that is one of its key benefits. Nothing frustrates me more than being behind someone on an incline and they begin.... to.... slow... down.... because they are not using CC and can't maintain their speed. The only reason not to use it on hills would be if the grade is very steep and you don't want the CC using your kickdown. As for decending hills - it's great for that, and will even apply the brakes if they are needed.