I think the structure it enforces is pretty minimal compared to many of the current JS frameworks. It doesn't take so long to get used to. Definitely much less overhead than redux in my experience. It boils down to 3 basic concepts.

I've made some moderately sized apps for it. Re-frame is incredibly productive and fun to use for a variety of things in my experience. The abstractions sometimes leak a bit (side effects can be difficult to make happen cleanly) but for most tasks it lends itself to really solid architecture.

I think they underplay how important the "form-3" components can be for complex apps (where you use more explicit lifecycle hooks) because JS events are frequently necessary, and they're required when you need to make use of raw JS libs.

Debugging in cljs is trickier than JS overall, which isn't surprising, is the real downside. But imo cljs fits a lot better into the reactive/immutable patterns that people are aiming for in the front end world these days.