Transactions are indeed “gone” in Ember data, but you can still use rollback on any dirty record:
cancel: function () {
var author = this.get('model');
author.rollback();
}
The rollback is thus on the record and no longer on the transaction.
See also http://discuss.emberjs.com/t/migrating-from-ember-data-0-13-to-1-0-0-beta-1-my-findings for some more info.
Good luck ! Marc