I was wondering the same thing and it appears that at this time you can only SYNC music/videos/photos to the iPhone. I'm sure they will fix this in a later update.
I was surprised by that as well...I hope they fix that, and provide the "disk mode" that other iPods have. I worked around it by making a Playlist on my Mac called "tunes for iPhone" and then just syncing that.
Yeah, this no manual adding music to the iPhone needs to be resolved immediately. It also needs to be handled for video. Come on Apple. Please do not take things away from us in a 500-600 dollar device.
The only solution I can see until a new software release is to create a special playlist and select that only that playlist be synced. This will enable you to in a way manually manage the songs/videos you transfer and retain the ability to listen to the artists individually.
Ok, I really wish I would have known that you can only sync playlists. I always have added my songs onto my ipod by putting them in the library first and then manually selecting and dragging the ones I wanted to add. I thought I found a fix-around to the playlist thing, but today all the songs I had added lastnight just magically disappeared!! So apparently if you do just sync the songs in your library you need to keep the songs there. Really stupid if you ask me!
This syncing playlists is all fine if all you want to do is sync to one computer, but if you want media from more than one computer, like a tv show that was purchased on a computer other than your synced computer it is not possible even if you move the media to the computer you sync to. You get a message that this computer is not authoriezed for this media or some such. I still own it. It's mine, who cares which computer I puchased it on. Apparently Apple does. I do not think this was through all the way.
This is a big problem. No manual management of files is seriously cumbersome. I'm not so sure they'll change it. AppleTV is the same thing, and they haven't changed that yet. I don't see it happening.
They apparently meant to add this, since the user guide reads:
You may want to prevent iPhone from syncing automatically if you prefer to add items to iPhone manually or when you connect iPhone to some other computer than the main computer you sync iPhone with.
To manually manage your syncing, open iTunes and from the iTunes menu select Preferences/iTunes. Then select Disable automatic syncing for all iPhones checkbox.
That only lets you manually sync instead of automatically sync - but you still have to sync. The users in this thread want to manually drag and drop songs, videos, albums, etc. on the iPhone like you can with the iPod.