well it is not that useful........but.
with my mild state of anti-lag i found that my car comes on boost quicker and honestly feels a bit faster when punching out of turns.
However, I dont use it for more than about 3 or 4 corners in a row as it really isn't that good for the motor and especially the exhaust wheel on your turbo.
It also changes the handling balance of your car when braking, actually it is probably the driver as "I" find, and this could just be me, that I change the way I drive to get the most out of anti-lag, I am more "point and shoot", which most of the time is slower than a smoother style.
Overall, I love the sound and would kill for an anti-lag system that gives me about 1 bar @2000rpm
but It doesn't happen on street cars and would not aid the lifespan of the motor/turbo. It only helps a bit on launch and twisty on-off driving.