Cruise control works fine for me, having a CVT gearbox, even down to below 30 mph, which I find very useful in urban areas, when I don't need to keep my eye on the speedo all the time.
It will also maintain the required speed on motorway hills, all that happens is the ratio changes and engine speed increases to suit the additional load.
I can well understand that these details may not apply to manual gearbox versions, where you would obviously have to change gear to maintain momentum.