SSS helps, but in any platform it slows the render down, and it can be a PITA to set up properly. Most of the plastic-looking skin is a result of more than one thing. Specularity set too high (trying to get that 'sheen'), no bump map used, and no luminosity. You wind up with flat, homogeneous, shiny plastic. 

Bagginsbill has figured out human skin better than anyone I've noticed here. His solution is one of the best I've seen, in any program, regardless of cost. CGTalk has seen a few good ones. It's not easy to portray, because we're all so familiar with it. Ever notice a greyscale render is easier to make look real than a color one?