I had an opportunity to try this out yesterday as I was on a reasonably quiet motorway and I must say that I was impressed - although it feels strange not being in control of the car. I am not sure how easy it would be to use on a busy motorway - perhaps one day I will build up enough confidence to try it!
One minor issue that I noticed was that it I was in, say, the middle lane with CC set to 70mph and the vehicle in front was travelling at 60mph then as you would expect my car slowed down. When I then moved out to overtake the car did not speed up until it was fully in the outside lane with nothing in front - whereas if I was driving "manually" I would be accelerating as I pulled out to overtake.
One minor issue that I noticed was that it I was in, say, the middle lane with CC set to 70mph and the vehicle in front was travelling at 60mph then as you would expect my car slowed down. When I then moved out to overtake the car did not speed up until it was fully in the outside lane with nothing in front - whereas if I was driving "manually" I would be accelerating as I pulled out to overtake.