I've been playing around some more..  I got a pretty good drape, and the hem is as close to the figure as I can possibly get without it sinking through..  But if you render fairly up close, you can see that there's a gap. 

The attached image shows a render where most of the light is coming from the back.  This can happen too with really sharp edges, but looks really prominent in this case.

Do you guys get this problem too with your clothes in a close up render?  If there's even the slightest gap between the clothing and what is over it, this seems to happen...

I think I'm going to go with displacement maps for the more subtle things like hems, and with a soft decorated for things that actually need some space over the figure, like collars and stuff like that.. And for some seams that sit between different fabrics.. :)