  In this paper we present a parameter estimation analysis of the polarization
and temperature power spectra from the second and third season of observations
with the QUaD experiment. QUaD has for the first time detected multiple
acoustic peaks in the E-mode polarization spectrum with high significance.
Although QUaD-only parameter constraints are not competitive with previous
results for the standard 6-parameter LCDM cosmology, they do allow meaningful
polarization-only parameter analyses for the first time. In a standard
6-parameter LCDM analysis we find the QUaD TT power spectrum to be in good
agreement with previous results. However, the QUaD polarization data shows some
tension with LCDM. The origin of this 1 to 2 sigma tension remains unclear, and
may point to new physics, residual systematics or simple random chance. We also
combine QUaD with the five-year WMAP data set and the SDSS Luminous Red
Galaxies 4th data release power spectrum, and extend our analysis to constrain
individual isocurvature mode fractions, constraining cold dark matter density,
alpha(cdmi)<0.11 (95 % CL), neutrino density, alpha(ndi)<0.26 (95 % CL), and
neutrino velocity, alpha(nvi)<0.23 (95 % CL), modes. Our analysis sets a
benchmark for future polarization experiments.
