Should I keep my stainless steel plumbing?

Apparently, the house we just moved into was repiped for some odd reason with stainless steel plumbing (yes stainless not galvanized or copper.) I have just replaced my bath tub and opened the wall and the new fixture is leaking. A plumber friend of mine has suggested replacing the entire section in the wall with copper. Should I keep the stainless or go with the suggestion? I see a lot of awesome answers and I want to thank you all. These answers kind of lead me to another question: I have used a dielectric union to attach (what appears to be) a brass fixture to these stainless pipes...I tried teflon tape (leaked) the tried putty which leaked again. How can I use the diectric union to join the two and avoid leakage? Should I use both together?Thanks again!