A primary use (at least for myself and many friends) is looking forward in time at various predictions. This is playing a map forward into the future to look at how an approaching storm or front is developing.
I wish there were better controls to do this. Two suggestions:
Advance or rewind the prediction in 1 hour increments in the same way you do with YouTube, Netflix, etc: controls on the left and right of the screen that step forward or rewind the animation. Dragging a finger back and forth along a tiny timeline is difficult, especially on a small screen.
Enable me to rapidly flip back and forth between a set of favorite views to display when looking at a map without having to go into menus. For instance, I’d like to look at my location, easily advance back and forth in time as a storm approaches (see comment #1), and then flip my view of the map between CAPE, Thunderstorms, Wind Gusts, Radar, Lightning, etc without exiting the map and go into menus. Possibly also flip between the models (at 1pm ECMWF looks like this and GFS looks like that) that the map is showing. A clear title at the top of the map of what I am looking at would also be helpful (there is one but it is tiny and does not reference the model).
The real value in Windy is the forward looking visualizations/predictions, versus the historical data (which is often available for free through a variety of sites).