I think it would be cool if it was possible to play syncronised on two units at once. My husband and I often listen to podcasts together, but in some places (at the bus for example) you'll need to use headphones to listen. This means we can't listen together, which is a shame.
In the good old days when mp3-players and phones had a headphone jack, you could use an adapter to let you listen to music together in two different headphones. But not anymore :(