I bought a Parker Fly Classic years ago and one of the big reasons was for it's stainless steel frets, since conventional frets made me mental. They just wore out too fast, the uneven intonation in different parts of the neck made me cringe, etc., and coupled with the fact that there are no good luthiers/fret-guys in my city, made me seek out alternatives. My Fly is ~12 years old and there is only the slightest wear on the 2nd fret G string, and I've played it a lot.
I have a Suhr S4 with stainless steel frets and won't buy a guitar without them. I love the silky feel and I think you get better sustain since the contact on a polished SS fret feels more 'positive'...no corrosion, just a nice mirrored smooth surface at all times, even outside on hot, damp afternoon gigs. As for the tone difference....I dunno, I get sweet sounds with both of them and that's good enough for me.
My friend just got a Wolfgang (or some new EVH guitar) with SS frets on it and he's never really tried them for any length of time, and he is completely sold on them now as well.