The low-energy excitation spectrum of HTS cuprates is examined in the light of thermodynamic, transport, quasiparticle and spin properties. Changes in the thermodynamic spectrum associated with the normal-state pseudogap disappear abruptly at a critical doping state, P crit = 0.19 holes per Cu. Moreover, ARPES data at 100K show that heavily damped quasiparticles (QP) near (π,0) suddenly recover long lifetimes at p crit , reflecting an abrupt loss of scattering from AF spin fluctuations. This picture is confirmed by μSR zero-field relaxation measurements which indicate the presence of a novel quantum glass transition at p crit . Consistent with this picture resistivity studies on thin films of Y 0.7 Ca 0.3 Ba 2 Cu 3 O 7-δ reveal linear behavior confined to a V-shaped domain focussed on p crit at T=0. The generic phase behavior of the cuprates may be governed by quantum critical fluctuations above p crit and the pseudogap appears to be caused by short-range AF correlations.