Author here. I have a Nexus 6. I hadn't tried the Google Play app until today so my observations were based on the sample app that I had built and another Flutter app that's in the play store called Newsvoice. I was under the impression that the Flutter sample app was just a github repo, and I didn't go through the trouble of trying it out.

The Flutter app in the Google Play store does lag for me during the first run of most large animations (nav drawer open/close, shared transitions, etc.). The second time those animations are run, everything is smooth. There must be some sort of caching in place for animations.

As far as I could tell, everything else seemed to be fine. Scrolling performance was good, as were smaller animations like checkboxes and switches.

Also do run in release mode for best performance. The default debug mode rather optimizes for developer convenience and hot reload cycles etc.

https://github.com/flutter/flutter/wiki/Flutter%27s-modes

I think the Gallery in Google play is outdated, better check the one from the repository to see the current performance