WTF

gistfile1.js

This works as an ArrayController:
Rapid.workflowCurrentApplicationController = SC.ArrayController.create({
    contentBinding: SC.Binding.single('Rapid.workflowApplicationsController.selection'),
    userBinding: SC.Binding.oneWay().from('Rapid.rootWorkflowController.content'),
    observeMe: function(){
      console.log('c '+this.get('content'));
      console.log('u: '+ this.get('user'));      
    }.observes('content', 'user')
});
output
c Rapid.Appl.....
u: Rapid.Ste.....

Change it to an Object controller:

Rapid.workflowCurrentApplicationController = SC.ObjectController.create({
    contentBinding: SC.Binding.single('Rapid.workflowApplicationsController.selection'),
    userBinding: SC.Binding.oneWay().from('Rapid.rootWorkflowController.content'),
    observeMe: function(){
      console.log('c '+this.get('content'));
      console.log('u: '+ this.get('user'));      
    }.observes('content', 'user')
});

c Rapid.Appl...
u: undefined