I'm glad I've got a steering damper on my 300.
I always raced the NSR with a damper, but I can't say that i ever wound it up that tight. However, I've ridden various NSR's round the track at 90% without a damper and didn't get into any serious trouble.
As Dave says, good for pose value, but maybe not a necessity. get one anyway though as it's always good to have extra things to fiddle with at the traffic lights. It annoys car drivers, 'cos all they've got is the volume knob on the radio.