Cool one Ed, it looks like that would be good for some kinds of Fabergé eggs too!

Another related technique is to take sweeps like that and intersect them with a base surface, then clean up some areas where you've got intersecting pieces and then trim the surface with that, that makes one smooth outer surface shell for the final result:
http://moi3d.com/forum/index.php?webtag=MOI&msg=3812.7

- Michael