  We show that the Ornstein-Uhlenbeck semigroup associated with a general
Poisson random measure is hypercontractive, whenever it is restricted to
non-increasing mappings on configuration spaces. We deduce from this result
some versions of Talagrand's $L^1$-$L^2$ inequality for increasing and concave
mappings, and we build examples showing that such an estimate represents a
strict improvement of the classical Poincar\'e inequality. We complement our
finding with several results of independent interest, such as gradient
estimates.
