Using the dielectric constant and conductivity at microwave frequency, we study the differences between highly conducting polyacetylenes and standard metals. We report that the microwave dielectric constant at room temperature for heavily iodine-doped Tsukamoto polyacetylene films is negative and of record size. This demonstrates that the highly conducting state is metallic despite the decrease in conductivity with decreasing temperature. The anomalously long transport time is attributed to suppression of both phonon and impurity backward scattering in a structure with an open Fermi surface. We analyze the temperature-dependent data using a model of three-dimensional metallic fiber segments coupled by weak links within which one-dimensional localization effects occur.