After watching your (cool!) youtube video, I see its actually a square/diamond extruded along a path.

A chisel bevel, or a 1 point bevel looks similar to what you accomplished. Basically, the surface meets at a point in the center, like a bevel with no curve. A more complex example is the 3d harry potter logo at the beginning of the movie. I'm not even sure "chisel" bevel or "1 point" bevel are the correct terminology, but it is what the internet commonly refers to it as.

Here is an example of what I'm taking about:
http://images2.wikia.nocookie....

Regardless, I'm still interested to know how you go about creating these shapes. The youtube videos are fun to watch.

thanks!

sweep curve