I personaly hope Google will replace Java with Dart at some point - it will be easier to switch for average Java dev (syntax) and there is already Dart for Android project - Flutter
It is stuck in an uncanny valley where the effects sorta looks like those of the platform, but are different enough to make the discrepencies very visible.
A simple list skips a lot of frames on my Nexus 6P, I can't imagine what I will look like on the regular user's phone.
None of the samples do anything interesting, they are just very tiny fragments of UI and even then there are many things missing.
Bringing Flutter up to speed with the native UI toolkit would demand a titanic amount of work