The other reactive/observable-based frameworks I've seen (eg Cycle) very much put the observable streams center piece, and I always felt that was distracting, and that nuances about how the underlying observable stream library worked quickly got in the way.
Solid still puts the components firmly at the center, just like React, but replaces React's state concept by fully reactive observable state, called "signals". You use them pretty much like you useState in React, but deep inside it's an observable stream of changing data, and you get all the finegrained update control that comes with that.
Also, I love how noun-heavy it is. Resources, tracking scopes, effects, signals. It's just like how React moved from "do this thing after the component updated" to "ok we have this concept called an effect", but extended to more topics such as dealing with async data loading, when exactly a signal is observable, etc.