Does anyone know what this feature actually entails? iMessage on my Macs has always synced for at least a year, including SMS (non-iMessage) messages sent from my phone.
Personally, every device I have (aside from my phone) has a different subset of messages on it. When they're on and near each other, they all get the same messages, but they definitely don't get everything all the time when off/out of range of my phone.
I suspect that the current setup is a best effort sync, while the full message backup exists within the iPhone backup.
iCloud iMessages would, I think, make that backup/storage a first class entity, separate from the phone's backup.
Oh yeah, maybe the syncing only happens from phone to Mac right now. I've never noticed or tested that, since my phone is basically always with me when I'm on my computer. I've had occasional issues with my Mac having out of order or missing messages, particularly when powering on my Mac after lengthy downtime, but it seems to resolve itself in a few minutes.
I have a desktop at the office, laptop and iPad at home and it's pretty amusing the way the messages between them do and don't overlap. SMS messages are the worst offender by far, but even the iMessages don't always end up on every device.
I've never noticed out of order messages on any device, even though it seems to be a pretty prevalent problem amongst the comments here.
From a user perspective, probably the biggest aspect of this is freeing up local storage. My iMessage database is 10 GB, my wife's is 9. That is not an issue for me, but there are still lots of 16 GB devices in active use.
