I am right now thinking about getting an 4G iPod nano (16 GB blue case) to either supplement or replace my 3G iPod nano (8 GB blue case). Some questions I need to ask: 1) How's the sound quality? 2) Is the battery life decent? I'm getting about 20 hours playing time on my 3G nano now. 3) How is the on-screen navigation compared to the 3G nano? 4) Will it work with the previous-generation Apple external iPod charger, the one with the fold-out electric plug? 5) Can I turn off the accelerometer mode?