I don't know if this qualifies as a bug or not, but Billings will only go to Address Book when you select File:Edit Client, even if the client was taken from Daylite. This is not a huge issue for me, because I have to sync between Address Book and Daylite anyway to keep my contacts up-to-date on my iPod, but it does mean I have to pay more attention than I want to when I sync, rather than just presume that the Daylite version is always the correct one. I would think this would be an even bigger deal for people who don't sync between Address Book and Daylite.