Worth it is subjective... We did the London/Paris ABD, and it was totally worth it. We had great guides. We got in and out of the major attractions without waiting in line. In addition to the major attractions, you get to do smaller things that are really special, like wine tasting in MontMartre, or Archery near Windsor Castle. You stay in upscale hotels. All your luggage is handled for you.
It may help you to know who ABD appeals to: On our trip, probably half the people were Medical Doctors and their families. There were also some business owners and then some miscellaneous retirees and Disney fans (like us).
The characteristic of Medical Doctors and similar professionals is that they have money, and they lack time. They don’t get a lot of vacation, and they have even less time to plan out a vacation so that they could save money. But to have someone else do all the planning, so all they have to do is show up and enjoy, and they get to see the sites and spend quality time with their family, that is magic.
So ABD is great and we enjoyed it a lot. But if you are in a profession where you have money to spend, but time is precious, ABD is a home run.