This feature can of course also be used to generate smooth rolling terrain, and GenSurf will take some of the drudgework out of editing those patches for you.
Curved surfaces come at a price, however.
With all the problems outlined below, you may wonder why curved surface support was added to GenSurf in the first place. The short answer is that curved surfaces work exceptionally well for small surfaces, but present many problems if used in a large open area. The screenshot below is of a 4096x4096 curved surface. Unless you're extremely picky the surface looks to be perfectly smooth. It has a fairly high price tag, though.