I have not tried MobX. It smells a bit too much like Aurelia, and I've been burnt a bit by Aurelia. More generally, too, things that make heavy use of ES2015 Proxies for side effects tend to make me pause, simply by nature of black/gray boxing those side effects, and also making it a little harder to control/throttle them in cases where performance matters more than "magic".

(Which is an interesting turn of events, personally, because I really liked Knockout ages ago, but its attempted successors in MobX, Aurelia, and even Vue leave me cold. I think partly because Knockout was so much more verbose and forced/needed a clearer "MVVM" separation simply by how "dumb" it was, whereas Proxies and Descriptors gives too much of an illusion that you are working with "plain" objects that don't need a clear "MVVM" separation until it is sometimes too late to fix a maintainability/tech debt hole.)