Hey Jean,
Yes I downloaded that example soon after I posted this question. It works well but when I clamp the values to the screen size the GUI label gets messed up when the object is behind the camera. I think that's where some math on the Z value comes in. Here's the snippet from the ObjectLabel script:
var relativePosition = camTransform.InverseTransformPoint(target.position + offset);
relativePosition.z = Mathf.Max(relativePosition.z, 1.0);
I'm going to try and recreate the script using standard actions today, i'll let you know if it works :-)
Simon