We describe applications of the rotating polarizer multichannel ellipsometer for three-parameter spectroscopy (1.4-4.1 eV), in which a full reflectance spectrum is acquired simultaneously with (psi, Delta), all in a time as short as 16 ms. Because data acquisition requires no significant effort beyond that of spectroscopic ellipsometry, the challenge of three-parameter spectroscopy becomes one of utilizing the third parameter effectively. Here, we demonstrate its utility in measurements either vs. fixed analyzer angular setting A for instrument calibration or vs. time for kinetic studies of nucleating films. In calibration, accurate results for the polarizer phase and analyzer azimuth scale correction can be obtained from measurements of the average reflected irradiance vs. A in the sample measurement configuration, irrespective of the value of Delta for the surface. In the kinetic studies of thin-film nucleation, the reflectance spectrum provides a criterion that allows one to identify the correct thickness and thus extract the evolution of the dielectric function with thickness. This procedure is demonstrated for Ag thin-film nucleation by magnetron sputtering on Si substrates.