You connect your transparency value to the opacity socket on the Surface Shader (top).
Then enable the Opacity checkbox on the Base Material node.
UPDATE: in new versions of Maya/ShaderFX you no longer have to enable the Opacity checkbox. Simply plugging something into the opacity input will make the material transparent
You likely also want to disable the "Depth Write" checkbox so that transparent object do not block the rendering of objects behind them.
By default objects render double sided in the Maya view, if you do not want this, disable the "Double Sided" checkbox on the Shape node of the object.
You should get reasonable results, but keep in mind that Maya's viewport is not a game engine and so sometimes sorting is not perfect. There are some improvements you can get by switching to "Depth Peeling" transparency algorithm. This can be found in the Viewport 2.0 settings dialog.
Unfortunately in Maya LT this crashes, but I believe this will be fixed in SP 1.
Even with Depth Peeling things are not always sorting great. Hopefully we can improve this in the future.