Over the past 30+ years of driving in countries all over the world and doing probably over 2 million miles in cars with cruise control, i use it all the time. It's become second nature
The early years were primarily American cars with auto boxes and armchairs. My first UK car with CC, in 1998, was a manual roadster with a straight 6 petrol lump, certainly helped economy when on long runs.
From those early CC where you manually controlled the CC, to my current car where you can use the various almost autonomous systems which leaves you to just steer the car, the CC has evolved.
In respect of towing a caravan, which is the relevant bit, I'm on my second tow car. They both have/ad the same 3 litre diesel engine. The last had a 7 speed autobox and the sat nag was linked to the CC. The current car has a 9 speed outbox and more autonomous systems I'll describe further on. They both have/ad Traffic Sign Assyst as its called that uses a camera in the windscreen to recognise speed limit signs and will if used match the speed to the limit automatically, just accelerates hard and decelerates equally as hard, so maybe not the most economic way of being driven. I don't use that when towing.
The CC on both have a 1mph flick function on the steering column lever for accelerate or decelerate, together with a 5 mpg increment as well. You can also use the lever manually in place of your right foot to control speed. The last car had no gear indicator. The new car displays the gear you are in. However at 60mph when towing it will not go into 9th as the engine speed is too low for the final gear. Solo it goes into 9th at about 63 mph. This is a function of the emissions regs to meet the targets by putting more cogs in the box, so any reduction in motorway limit as recently muted will actually increase emissions as 9 speed cars will not get into top at 60 mph.
The new car has a system called Distronic Plus that allows you to set the distance from the vehicle in front and maintain the distance up to a pre set speed. This is a radar based system with the big black solid badge in the grille. This is particularly useful when towing, I find. Solo it makes the journey more relaxing as I set the speed at the posted limit and orf we go. It's been interesting to try out various scenarios. I did the same journey a few times. Initially I did it at my previous car cruise speed in the new car, then with the system above and found time wise the journey overall was the same, and economy was far better at the lower speed. So I now set the system to the speed limit. So my behaviour has changed. Who says you can't teach an old dog new tricks!!
When towing on the motorway for example I set 60 mph. If i come up to a slower moving vehicle the car maintains the safe distance behind until I can find a space to pull right and overtake up to 60. Interestingly when solo and at 70, cars come racing up behind, overtake and invariably throttle off and drop their speed by up to 10 mph, which my car reacts to, then you accelerate again. It may be a macho thing about overtaking a big Merc with a fizz bang boy racer car
This system also brakes the car automatically should I want it too, just a bit harder than I would if on manual control.
On the A303 at Sarum there is a speed camera. going westbound down the hill, the car tays at 70. others brake very hard as they see the camera. Eastbound lots of drivers race off from the Amesbury roundabout after invariably being in a queue past Stonehenge, go round the right / left switch and start the incline, then see the camera and brake hard losing all inertia for the big climb. I cruise past at the constant 70 and eat the hill with ease the gearbox dropping to 7th on the way.
Further advancement toward fully autonomous will bring calmer driving as you will basically travel in convoy at constant speed at constant spacing, which can only be a good thing. Or have i finally calmed down with age and find driving is not the fun it used to be?