This seems to solve my problem of not having strong database auditing and row-level / column-level permissions -- I'm paying for Oracle, why not leverage the database to the fullest extent assuming no concern for lock-in.
What else isn't going to work? Seems like a lot of this should be in appservers -- the feature has been around in Oracle for 6+ years now but the information about it sparse (and a lot of searches are bad because of the generic term "proxy")