Take a closer look at your edges:

You can see, that you havn`t changed the shape of your box as if it was a chamfer-box. And you have nice "natural" non-perfect edges !

Ok, so what does this give to us in our daily CG-Business ? Here you can see a part of a model with no smoothing on it:

With the smoothing modifier on the object:

as you can see : hard, geometrical object with nice smooth beveld edges :-)

These edges are solid-beveld with additional edgeloops to keep the shading-gradients at the geometrical edge.
This technique offers modelling with a small count of polys and a nice beveld edges, too.

Hope this tutorial isn`t too basic and it helps understanding the technique of Poly-Smoothing. It is very usefull for technical stuff not for organic objects....

Here is a maxfile (max6) , i prepared for download. It is self explaining when you open it :-)   solid_bevel.zip

Best regards,

Thomas