Last night I had the vanilla shake with a good 2 tsp of instant espresso powder (Carte Noir Expresso) and ice cubes, and it was lovely -- like an iced coffee. I made it quite strongly coffee-flavoured, though. My husband tasted it and said you wouldn't know it was diet food at all.
As a slave to my Nespresso machine I don't drink instant coffee, but I had bought the jar with the intention of making a Nigella Lawson recipe for coffee ice cream. Then I spontaneously went on the Exante diet on the spur of the moment, so the ice cream idea was abandoned. I'm pleased to find some use for the coffee powder, though. I have also tried it in the chocolate shake, as a mocha, and that was nice too. I will definitely have both combinations again.