I've been synchronizing my Nokia 5800 with MM for over a year now. It had been a while so I wanted to sync again just now before going on a trip. When first connected it says there is about 1.5GB available and I select auto-sync. I expect minimal interactions with the device as I haven't updated my library in some time. After munching on the 5800 for a while it tells me it first needs to remove all my data before it can copy. That seems to negate the whole concept of syncing. I did not want to get stuck so I told it 'ok'. I then synced again. Now I have 1.7GB available. I guarantee you that my playlists are virtually identical. I then added another album and re-syncd. This time luckily only the required files were copied.
How do I make sure that next month when I sync again it doesn't force me to erase everything before syncing? It probably removed a few podcasts I had downloaded on the phone and there really was no reason for that.
PS I just upgraded to 4.03 from a 4.0 beta. I'm a life time member.