Most analyses and simulations of all-optical guided-wave devices are based on Kerr nonlinearities. In practice, most media exhibit index saturation and reduced absorption with increasing intensity in wavelength regions where their nonlinearity is usefully large. Such non-Kerr-like behavior can deteriorate the all-optical response of guided-wave devices such as nonlinear Mach-Zehnder interferometers, directional and distributed couplers, and nonlinear gratings. Positive effects of saturation with regard to an integrated-optics beam scanner are mentioned.