The ASDEX Upgrade tokamak (AUG) employs a 60-channel super-heterodyne radiometer for the measurement of second harmonic, X-mode ECE along a horizontal line of sight near the tokamak midplane. The measurements lead to radial electron temperature (Te) profiles, following a well-established technique [1]. The front end of the radiometer, including the lens, polarizing grid, and waveguide antennas has been described in [2]. The microwave receivers and down-converters, power splitters, band-pass filters, Schottky diode detectors, and video pre-amplifiers conform to the standard approach described in [1]; the performance of these sub-systems and the properties of given plasma discharges lead to Te spatial resolution of 1-2 cm. A new data acquisition (DAQ) sub-system with sampling rate 1 MHz has recently been added to the system. The original DAQ with sampling rate 31.25 kHz has been retained, in parallel, for validation. Details of this upgrade and initial plasma measurements comparing the old and new DAQ have been presented in [3]. Briefly, the upgrade features new amplifiers for each radiometer channel, each with 2 MHz bandwidth and software programmable gain (from 1-100); the latter allows the sensitivity profile of the radiometer to be optimized for each plasma discharge. The fast DAQ allows measurements of plasma phenomena on the MHD timescale, such as neoclassical tearing modes (NTMs), and the role of ECE in a real-time control loop on AUG for the suppression of NTMs via targeted deposition of electron cyclotron resonance heating (ECRH) is described here. Also, in a related ECE technique, MHD activity during the current ramp-up phase of certain AUG discharges is being studied in an effort to constrain qprofiles by locating modes on rational surfaces.