Given that even after a major overhaul, Linkedin's web interface is sub-par wrt. UX as well as performance, I am not sure Linkedin's endorsement really contributes positively towards popularity of Ember.

Totally agree. I love ember but linked in’s new ember interface just makes my Laptop fans spin like crazy.

I worry because I know they’ve hired some of the most talented folks from the Ember community (people who care about performance and scrolling jankyness). This is not a knock on them, but it is worrying that even the best of the best may struggle with larger, more complex apps.