While it's labeled alpha, AFAIK it's fully available for public use and it's fairly functional.

Functional but fairly buggy still. For example it misses a lot of button taps because there is a universal move threshold of about 2mm. And if you want to do anything other than display widgets in the app (e.g. display notifications), you're going to have to write a plugin for it.

Unless you want to run your code on the web as well, I guess ...

If you write the web version of your app using AngularDart, you could probably share a fair amount of code between the two.

Not everyone wants to impose 2nd class UI/UX on their users.

Performances are really far off still. 120 fps ? it can't do 30 at the moment.

(and fps is a pretty awful metric on mobile, what matters is the number of frame dropped)