i never had a suntour, but i have had a nankai for about 4yrs now, and 9 months of that is with the profile shell...i have had no problems with the hub at all. I did have a minor thing with the dustcover rubbing when i got the profile shell, but without that its been workin as good as it did with the regular shell, ive had zero problems with the nankai.
I have heard though from i think it was TJ and a couple of others that sometimes when doing rear wheel spinning tricks, when there is alot of side to side pressure, it would engage. But other than that, i haven't heard anything bad about nankais function wise.( some dont like the little extra weight)