I only know of one genuine 4WS fault and thats a dry solder joint basically. I had my car for 10+ years before it ever showed up and it was sorted that night, it's really not a big issue.
Like anything, maintenance is key. The other 'faults' that people like to harp on about are usually not the 4WS at all, but a wheel sensor or similar. Which, IMHO, is a bit like ripping out your brakes, because a bulb went.
