  This paper explores single field inflation models with a constant, but
arbitrary speed of sound c_s, obtained by deforming the kinetic energy terms to
a Dirac-Born-Infeld form. Allowing c_s<1 provides a simple parameterization of
non-gaussianity. The dependence of inflationary observables on the parameter
c_s is considered in the leading order slow roll approximation. The results
show that in most cases the dependence is actually rather weak for the range of
c_s allowed by existing bounds on non-gaussianity.
