I still don't have much experience of TS4 ghosts, but by now I have dealt with them like this. If the deceased sim wasn't that important to my sims (or me) I just send their spirit away quickly, but if they were dear to someone I like to keep the ghost around till my sim is ready to let them go. So I'm kind of giving my sim time to accept the death and chat with their loved one. If the sim doesn't believe in supernatural I see it as a psychological thing that is going on in their head, but if they believe in ghosts I play it so that they really see the spirit and the spirit is there (other sims around them might find it weird though).
I currently have only one sim, Tessa Pancakes, who really believes in ghosts and she is turning the Pancakes home into a haunted house :D She doesn't want to let her mother or husband (Hugo Villareal) go and keeps giving them offerings and chatting with them. She might even ask Hugo to move in.
I think the ghosts are quite a fun addition, at least they are quite easy to get rid of if I don't need them. I might prefer not to see them in community lots though. I liked it when the ghost of Hugo called Tessa and congratulated her on giving birth to their child, especially because that was the first time Tessa heard of Hugo after his death and it made her wait for his visit. Anyhow, that was the first time a ghost has contacted my sim via phone, so if that happens really often and with a different sim it most likely gets annoying. I might treat those calls as prank calls then.