Superb, and very flexible!

It is the most useful calendar available for iOS.
It does have any learning curve, however all the advanced features can be turned off and is still better then the others.

I have a number of advanced features turned off so that I can stick with the internal Apple calendar.
The wealth of tools available even than is wonderful.

framework4 about Informant - Agenda, Tasks, Notes Planner, v4.94