The rumour has been confirmed by Steve Jobs, the 4th generation iPod nano is skinny again and features an accelerometer for automatic switching between portrait and landscape modes. Holding the center button during a song brings up the Genius menu.

The new nano is tall like the original nano, but it’s also curved like the iPhone. It’s available in 9 colors (black, silver, purple, blue, green, yellow, orange, red and pink). Batterylife would be 24 hours of music and 4 hours of video, sounds similar to the old nano.
A new feature is also the built in microphone for voice memo’s.
According to apple the new nano is arsenic-free , bfr-free, mercury free, pvc free, and “highly recyclable.”
The price will still remain the same, 8GB for $149 and 16GB for $199.