The General Agreement on Trade in Services (GATS), like the Marrakesh Agreement Establishing the World Trade Organization of which it is an integral part, will soon celebrate its 20th year of existence. What should we make of it? The vast majority of significant developments under the GATS have been the result of decisions by WTO adjudicatory bodies. Even though there has been no avalanche of disputes under that agreement, a critical body of case law touching upon several key issues concerning the interpretation and application of the agreement has emerged on what is arguably the most complex and opaque of WTO agreements. While some of these issues, such as the relationship between the market access and national treatment obligations, were the object of lengthy discussions by negotiators with a view to providing (negotiated) clarifications, it is through dispute settlement that the job was done. This should be a surprise to no one, since it has become obvious that the membership of the WTO is so large now that consensus on anything meaningful is extremely difficult, if possible at all. One might well need to go back to the Tokyo Round code formulae, the departure from which was hailed as a great success with the entry into force of the ‘single undertaking’ WTO Agreement. The purpose of this chapter is to review and provide an assessment of those key and fundamental issues that have been addressed, determined and settled to date via GATS dispute settlement. Have WTO adjudicatory bodies succeeded in making good sense of grey areas, thereby adequately complementing the work of negotiators whose task is, ultimately, to work out the best possible compromise? This chapter will allow one to determine whether the GATS is like a good wine – getting better over the years – or not.