Could this be a good sign?

We brought home a new kitten on Saturday and have her comfortably isolated from the resident cat. Both kitties are doing perfectly fine on their own. At first of course the resident cat did a lot of hissing and growling at the door, and doing a few 'scent exchanges' really sent her into hissing fits.

Now though, much to my surprise, the resident cat doesn't seem as bothered by the scent. She doesn't hiss or growl at the door unless she hears the kitten meowing, or if we open the door and she actually sees her (in which case there is a TON of hissing/growling again). And doing some scent exchanges now has her doing pretty minimal hissing.

It's only day 3...is this a sign that things are going well, or is it pretty normal that they get used to the scent quickly but are still very slow to actually accept the newcomer in 'person'?

Sounds like progress. It took my Chilsa a while to want to have much to do with the kittens when I first got them. No aggressive behavior (very fortunate: I was in an open floorplan apartment then--the only room with its own door was the bathroom) but he would hiss at them to get them to leave him alone. But he went from that to accepting them and practically adopting them.