Hmm, if we can optimize the reactive state management in all web apps, that sounds cool.

If this is to be a base for VueJS, it should handle deep changes. They have a note about support Map and Set, but being able to to control depth is nice in VueJS. (I'd say watch() should be deep by default, since non-deep is an optimization that can lead to accidental inconsistent state.)

Streams. Generally, I find RxJS backwards. Usually you just need "state", so that should be the easiest thing to implement. But I can't deny that the programming model is beautiful. Standardizing "state" without also considering streams seems odd to me. The "computed" creates a pipeline of updates, very similar to one you'd do with a map over a stream. If RxJS didn't already exist, I probably wouldn't have cared about this duality.

Async. Sure, signals can be synchronous, but Computed should definitely play well with async functions. This is a big shortcoming in VueJS (that people work around on their own.) That also implies handling "pending computation" gracefully for debuggability. I see there's a "computing" state, but this would have to be surfaced to be able to debug stuck promises.

Exceptions. I like the idea of .get() rethrowing exceptions from Computed. VueJS is a bit vague on that front, and just stops.