As we speak it is used in production by many companies. Click this link to see them all:

https://github.com/emberjs/ember.js/wiki/Production-Deployme...

Shopitome is a very fresh deployment using emberjs based on this tweet sent today:

http://twitter.com/inkredabull/status/268017623428657153

http://www.shopittome.com/threads/signup

A few non trivial companies using emberjs in production are:

www.zendesk.com

http://www.squareup.com/

http://livingsocial.com/

http://www.groupon.com

http://www.desk.com/

http://basho.com/

http://travis-ci.org/

http://www.gooddata.com/