Having used mobile iTunes on the Motorola SLVR for a couple weeks, I am fairly impressed.

When syncing tracks from iTunes to the SLVR, it knows when you have partially listened to a track. This is hugely important when listening to long tracks, such as podcasts.

The big drawback comes when going the other direction, since no data it sent to your Mac regarding track location.

Here is an invention for Apple.

Automatically transfer track data from the mobile device to the Mac, kicking off the track currently playing on the phone when you are within range or initiate the sequence.

For example, I am listening to a podcast in the car, walk into the house and the device automatically launches iTunes and starts playing the track I am listening to, from the location in the track last played on the mobile device.

They could use bluetooth to send over the data quite easily, or perhaps the infrared port on the new MacBooks.

Obviously many nuances would need to be customizable. Such as whether to merely queue up the track to the location vs. actually playing the track, stopping the mobile device when the desktop start playing, etc.

I hope someone over at Apple is working on just such a feature in their rumored iPhone.