By the way the reason you are seeing some edges hard and some soft in unsmoothed mode (1-key) is that maya applies a 30 degree smoothing angle to the object when you combine poly surfaces and so some edges are getting softened.

However the default poly edge display mode is standard so you see all solid lines when you look at the wires and the open gl renderer displays all kinds of shading artifacts. This is why I harden all my poly edges as I am modeling.

Hardened edge normals will not cause creasing when you go into smooth preview mode because all the edge normals are softened after the model has been subdivided 2 times. So the only creasing will be as a result of either bad geometry or edges that are very close together.