I didn't see the author at any point question the performance of their JS framework. More specifically, it seems like the author is using Ember for their apps. My (very rough) understanding is that Ember tends to have a lot of issues running on V8. Due to the way Ember is written, V8 tends to have a hard time optimizing for it.
Where the other libraries all cluster around the same framerate, Ember is running in the single frames. I know that benchmarks can be written in a way to make one library look pathological so this is just one data point, but I wanted to throw it out there. I agree that it would be great if V8 and Ember played better together :)
Looking at the dbmon benchmarks there's a big difference between Ember performance: http://mathieuancelin.github.io/js-repaint-perfs/ember/
And the performance of other frameworks/libraries:
Angular: http://mathieuancelin.github.io/js-repaint-perfs/angular/
Polymer: http://mathieuancelin.github.io/js-repaint-perfs/polymer/
React (optimized impl): http://mathieuancelin.github.io/js-repaint-perfs/react/opt.h...
Where the other libraries all cluster around the same framerate, Ember is running in the single frames. I know that benchmarks can be written in a way to make one library look pathological so this is just one data point, but I wanted to throw it out there. I agree that it would be great if V8 and Ember played better together :)