There are plenty of WRXs and Evos running anti-lag over here, yes long-term it is harmful to your engine. However all these cars (running either Autronic, Motec, PowerFC etc ECU's) have a switch to enable or disable the system - it is NOT something they run everyday on the street during normal driving.
Therefore you can minimise the wear and tear of it by only using it in certain applications - flame throwing contests

, drags, track etc.