Fitted one to my stock 172 last week. It has reduced the 'floating' I got at high speed, and also changed the feel of the front end.
The outside front used to sink and then slide under heaving cornering. With the ARB on it sinks less, and now feels to grip a lot more and not wash wide. I have also got some squeeling comming from the rear tyres as well as the front, so I assume its encoraging the rear to move more than without.
I cant say its made a massive difference, but its definately reduced the tendancy of the front end to understeer and sink down. Coupled with some new springs it should make an overall improvement for me.
(Testing was carried out at Cheddar Gorge
)