The Create 3D is a pretty slick tool, but beware of the condition of the 2D data you are using. I have run across numerous situations over the years where the 2D data is garbage either because of the way it was originally created or how it was changed at some point during its life.
Too many times lazy people go in and change dimensions without changing the geometry. My advice would be that if it is something very important, take some time to check out the geometry to make sure it is accurate. It is the old garbage in, garbage out thing.
I have been burned enough times that I am very wary of any 2D geometry, unless I created it personally, and then I am still not sure I trust it! ;-)
Bob