  Gravitational lensing distorts the cosmic microwave background (CMB)
temperature and polarization fields and encodes valuable information on
distances and growth rates at intermediate redshifts into the lensed power
spectra. The non-Gaussian bandpower covariance induced by the lenses is
negligible to l=2000 for all but the B polarization field where it increases
the net variance by up to a factor of 10 and favors an observing strategy with
3 times more area than if it were Gaussian. To quantify the cosmological
information, we introduce two lensing observables, characterizing nearly all of
the information, which simplify the study of non-Gaussian impact, parameter
degeneracies, dark energy models, and complementarity with other cosmological
probes. Information on the intermediate redshift parameters rapidly becomes
limited by constraints on the cold dark matter density and initial amplitude of
fluctuations as observations improve. Extraction of this information requires
deep polarization measurements on only 5-10% of the sky, and can improve Planck
lensing constraints by a factor of ~2-3 on any one of the parameters w_0, w_a,
Omega_K, sum(m_nu) with the others fixed. Sensitivity to the curvature and
neutrino mass are the highest due to the high redshift weight of CMB lensing
but degeneracies between the parameters must be broken externally.
