Logged In: YES 
user_id=103811

I realized that the exception throw behaviour is more fundamental to the underlying implementation than may have been indicated in the above description.  In particular, throwing an HTTP exception when handling a 401 is key to making the various Authentication Handlers work.

I still feel that the behaviour should be normalized across all requests such that the callee is responsible for determining error conditions or, at the lest, has access to the same data in a relatively similar format upon success or failure.