iTunes 10.6 Auto-Conversion
As you may know, when you sync an iPod, you can have iTunes automatically convert your music files to a lower bit rate, so you can save space on a portable device. Previously, the only choice you had was 128 kbps. But iTunes 10.6 offers three choices: 128, 192 and 256 kbps.
The auto-conversion feature was originally restricted to iPod shuffles. Now, I use it to fit almost my entire music library onto an iPhone.
