  We examine various aspects of the conjectured duality between warped AdS$_5$
geometries with boundary branes and strongly coupled (broken) conformal field
theories coupled to dynamical gravity. We also examine compactifications with
5-d gauge fields, in which case the holographic dual is a broken CFT weakly
coupled to dynamical gauge fields in addition to gravity. The holographic
picture is used to clarify a number of important phenomenological issues in
these and related models, including the questions of black hole production,
radius stabilization, early universe cosmology, and gauge coupling unification.
