It's made out of aluminum, even thinner than the first gen. They're bringing back colors (like the mIni). It looks similar to the Mini, actually.
Battery life increased from 15 to 24 hours, gapless playback, instant search like the big iPod, and quick scrolling. Comes with the new headphones.
Comes in three models, 2GB model in silver, 4GB in silver, pink, green, blue, and 8GB in black.
$149 for 2GB, $199 for 4GB, $249 for 8GB model. Double the storage for the same price.
New packaging is 52% less volume than the old iPod nano. It's more "environmentally friendly".
All three are available today.
The new nano works with the charger, the armband, lanyard, and works with the Nike Shoe (I don't know if it works without the adapter or if that's still in there. I think it's still necessary.)