I like to sync my files with PowerFolder. I can directly sync my computers in LAN or online and don't need to upload them to any service provider. ...And it works perfectly between my Linux and Windows box. I think a Mac client is also available.

Sorry for posting this again, but:

Try PowerFolder. It's a mature alternative:
* The software works since 2003
* It gets actively developed
* It's open source - a free Basic client is available
* There is a commercial Pro client with advanced security and connectivity features and 5 GB Online backup space

http://www.powerfolder.com/

Best regards,
Christian