Certainly the work they do in revealing war crimes that never would have otherwise been publicly known is important, and certainly it's fun to see politicians exposed for chicanery, weasel speak, and outright bullshit, but these are all things we more-or-less knew were going on before. The most important thing that Wikileaks does is to demystify the State's power over life and death, deflate the mythical archtype of the Jason Bourne/Jack Ryan style technosuperman, expose our fascination with the modern war making and dirty tricks business; with all of its fantastic technology and intriguing code languages, as nothing but the most childish servility.
To read through the Wikileaks files on war, peace, diplomacy espionage and the rest is to discover that there is no 'great game' going on, no taut psychological thriller keeping you on the edge of your seat. Decisions over the lives of hundreds or thousands or people are not made with cameras slow-panning the tension on the faces of various sundry officials while the leader cites Plato in a speech on the terrible import of what he is about to do.
No, the relationships between the nations of the world, whether malevolent or benign, are determined by very flawed and perfectly ordinary people, people who will or won't order a bombing that kills thousands if they decide that this is the most personally convenient choice to make, the one that will prevent the need to make more decisions later. There is a cliquish and banal familiarity between geopolitical players. Tensions between nations rise and fall based on the personal jealousies between leaders and diplomats. It's all so routine and human, to the point where I think the powers that be would actually prefer that they've been caught in some horrible scandal, some Illuminati-style conspiracy, because at least there's still some aura to being sinister. But no, the great leaders of the world are all a little myopic and more than a little dopey, but that's really all they are.