SuperSync had a nice booth at last week's Macworld Expo 2011 conference. In addition to a demo of the software on our livestream, we also chatted with the developer about how SuperSync (which allows you to share and view multiple iTunes libraries across PCs and platforms) was doing lately. The most recent version is 4.01, a bugfix release that also added the ability to browse video across libraries and support for multiple formats.
SuperSync is not a cloud service; it's designed to control and view actual files across multiple computers rather than keep them up to date with a cloud server elsewhere. You can listen to music stored on other iTunes libraries with the app, but its main job is to keep everything current in
