I think it's right that K1 P1 in provisional won't unravel. I don't know, because I actually cast on directly into K1 P1 for my rib (Montse Stanley calls it "tubular cast on" in The Knitter's Handbook and describes it immediately after provisional cast on). I like the edge a lot on rib, because it just flows into the rib and has the same stretch. If the rest of the pattern is not rib, it probably will look weirder.