1. It's not running Ember in production mode which is much faster.

2. It's running an older release candidate version of Ember.

3. It is purposely wrapping individual events in run loop executions rather than just letting ember figure out when you put things into run loops.

I re-ran the benchmarks with the latest production mode Ember.js and removed the incorrect run loop usage got the following results:

https://gist.github.com/eviltrout/8058560

It's still slower than ReactJS but much less so than before. In fact it's now #3 in that benchmark suite behind ReactJS and Backbone (and much faster than ReactJS in the completing benchmark), although I wouldn't be surprised if the other frameworks were set up as incorrectly too.