i have heard of people finding their steering to be heavier after fiting the lockbar but then there is no movement in the rear wheels anymore
when i fitted the lockbar i went down and got a four wheel allignment and afterwards found the car to be more predictable when cornering under power (in a controlled enviroment of course) and noticed no difference to the feel of the power steering
the only thing that changed was the hicas light stayed on easily fixed by removing the globe
have a look in the diy section of the forums im sure all this will have been covered along with a guide on how to fit the lockbar