I don’t think my observations are relevant for those who sync Timeline with Scrivener or Ulysses - they will have a different balance of advantages and disadvantages.
Historically I have used Aeon Timeline simply to record detailed timelines in situations where having that available and correct is important. The narrative/outline and mindmap views weren’t options. Accordingly, I only entered events, characters, locations etc where necessary. I find entering data easier in AT3, which brought the temptation to enter events partly because they might turn out to require a timeline entry and partly as a more complete record. This also makes them accessible to the narrative view.
However, I quickly realised that this was extra time spent, with no payoff. The event list became more cluttered and harder to work with. So I have reverted to entering as and when needed only.
The next question is that, given I have no sync, what advantage do I have from using the new views? Easy selection of events for narrative cards is one, though that doesn’t save any time.
What are the disadvantages of using Timeline narratives? The big one is that it presents a much poorer structural overview of the narrative than other options (eg Plottr, Jutoh etc). I can glance at the others and see what’s needed very quickly - they have more visual impact. If I have added a ton of information to Timeline, I can have more information dense narrative cards but most of the time that will be overkill for me.
So, in my situation, I’m not sure that the narrative, outline or mindmap views will be very helpful for most of my writing. The big exception will be for writing based on research, where the information will have been entered in the program. For those who like to have every detail recorded, these views probably offer greater advantage.
The big advantages of Mindomo and Plottr are speed, simplicity and most importantly more visual impact.