We very much enjoyed Artist Point. It isn't on the top of our favorites list in the sense that we don't make the trip over when we're not staying at Wilderness Lodge (we don't rent a car and it can be a pain to get to on Disney transport), but I'm very happy we tried it on our stay there. The salmon was excellent, as was the sweet potato side, and DH enjoyed his buffalo (strip loin, I think) so much that I didn't even get a taste.
Yachtsman is our least favorite signature overall, not because it was bad but because it is just a nice steakhouse, not really any different from places that we can go here at home. The food was good but not outstanding, and none of us feel any overwhelming desire to return.