the main reason for the powersteer is as Andrew has said "excessive feed back".
I had a few instances when the car was understeering but when it found grip snaped the wheel back violently, and with the Mota Lita wheel it hooked my thumb and bent it back. Ouch
NOw the powersteering rack acts like a dampener, and this no longer happens.
There was also a better wheel ratio, less turns from lock to lock, have you ever tried to quickly turn lock to lock, hitting your elbows on the sill. Not a very comfortable manouver.
The very obvious improvement is in slow speed "parking" .
I have found it to be really good on the track you are very relaxed driving not muscling it arround. After a dozon laps of wakefield you can really feel it in your shoulders, with the power steering it is easy.
I recomend it, most modern race cars have powersteering.
Phil