I can apply fractal noise to a spline abject, no problems there.  And I can apply fractal noise as a bump map, which warks fine.  I can even use the displacement paint tool on a vertex object...works a treat.  Just ant kind o pattern (cellular for example) used on a displacement shader for vertex objects stuffs the whole system.

Is this just me?  can others use fractal displacement on vertex objects with no worries?