This iPhone/iPod sync option is new to a recent version of iTunes. It’s incredibly useful and helps cram a lot more music into a device’s limited space, especially if you have a lot of high-bitrate songs.
It’s strange when you download music on the device then connect it with iTunes. The data transfers from the device up to iTunes at full quality then is converted to 128 kb/s and sent back. This makes sense, but just seems a bit odd.
(Reblogged from Marco Arment)