From the doubleTwist website:

We started doubleTwist because we were disappointed by the quality of software applications offered by the major device manufacturers. We wanted to build a universal media application that helps people quickly and easily play all their stuff, on all their devices and share their experiences with all their friends.
Our vision is to provide for media what the browser achieved for the web: a single, streamlined interface that connects to any device, media source or network.

The application most notably allows you to sync content with other devices besides an iPhone or iPod with the elegance of a Mac.  I haven’t played around with it enough to get a good feel, but looks extremely well put together so far.