Allegro: noise performance and the ongoing search for gravitational waves

The noise performance of Allegro since 1993 is summarized. We show that the noise level of Allegro is, in general, stationary. Non-Gaussian impulse excitations persist despite efforts to isolate the detector from environmental disturbances. Some excitations are caused by seismic activity and flux jumps in the SQUID. Algorithms to identify and automatically veto these events are presented. Also, the contribution of Allegro to collaborations with other resonant-mass detectors via the International Gravitational Event Collaboration and with LIGO is reviewed.