Stainless steel frets are apparently are right bugger to dress, due to the hardness, so I'd hate to think what these are like.
I've got SS frets on my warmoth guitar, no difference in sound and not much difference in feel (the main advantage is it reduces the chances of my nickel allergy flaring up). I also once had a P bass refretted with SS - on this instrument there was a noticable increase in fret clatter.
So, I'd say, if your hands are ok with nickel... stick with nickel.