Users' feedback is a vital component of the success of any service organization, but response rates are usually not very comforting and receiving feedback on a regular basis is a rather challenging task. This article presents the main findings of the Feedback Campaign we launched in early 2007 and attempts to analyse its significance. The Campaign targeted all Principal Investigators of ESO Service Mode programmes approved over the period 2001 - 2006. Possible future evolutions of this type of campaigns are briefly discussed, based on the experience we have gained.