I'm gearing up to do a somewhat-custom guitar and it's going to have stainless frets. My only experience with them is on a couple older Parkers that I played, and I was quite impressed.
About the stainless strings...I would stay away from them unless you're using them with stainless frets. For the same reason that stainless frets last so long with normal nickel-steel strings, stainless strings will eat nickel-steel frets. A guy I know was using stainless strings on a brand new Jem and I couldn't believe the fretwear on that thing after only about a year.