We have measured the magnetoresistive response of submicron NiFe/Ag giant magnetostrictive (GMR) devices as a function of current density and field angle. In addition to magnetostatic broadening, we observe large lumps in the magnetoresistive response (Barkhausen jumps) due to domain switching. These effects lead to irregular device-specific magnetoresistive response curves, The large Barkhausen jumps are more pronounced at low current density while at high current densities the response is smoother due to self field stabilization. The detailed structure of the Barkhausen jumps is very sensitive to the angle of the applied magnetic field. These effects are general properties of a wide class of GMR materials that rely on incoherent reversal of many small magnetic domains. We compare the experimental data with a micromagnetic simulation which incorporates a phenomenological GMR transport model. The model qualitatively describes the experimental data and provides insight into the detailed micromagnetic behavior of these films.