My Volvo accelerated smoothly with CC, pretty much as I would have done myself. But what it would do, that explains why mpg is not so good with CC, is it would change down on a hill to maintain speed. I, on the other hand. would back off slightly as I approached the crest, happy to slow by 5 mph or so and not make the change. I have never ever driven a manual with CC (I have driven them, I just never used CC), so I am not able to speak on their foibles.
Driving an automatic, with CC, is mind sappingly dull, and I could well see how drivers nod off. The more driver "aids" we have, the worse it will get.