I don't find IFs creepy myself, just annoying which is why I tuned them out using Retuner. But there is something I like about the ones I've seen pictures of in other players' games who have been made real. They seem to have an element of sadness or melancholy to them that other sims don't have, as if they have "seen" things while quietly sitting on a shelf that no sims should have to see. It's been pointed out to me that this is all in my mind and IFs who have become real are just like any other sims, and those who have done so are probably right.
But I'm just not patient enough to go through all of the steps involved in nurturing that IF friendship until the possibility of them becoming real even exists. Will revisit some day. :)