I've not got round to softbody yet with IrrPhysx... after I did the cloth stuff I assumed the softbody would work in a very similar way so set about doing it and then found that it was similar yet different and used tetrahedra instead of polygons... or something like that... fairly bizarre and was going to require a fair bit more work to get it setup nicely, so I gave up for the time being until I had more time to work on it!
I don't know if anyone else has Physx softbodies working with Irrlicht.. Not that I've seen I don't think.