Yes, synchronizing with the iDisk is possible. You can access it directly using the WebDAV protocol. On Mac, you can also mount it and access it as a mounted volume rather than via WebDAV.
Here’s a sample WebDAV URL for the iDisk: https://idisk.mac.com/youridiskname/
Replace youridiskname with your username, i.e. the first part of your @me.com or @mac.com email address. Do not include @me.com or @mac.com. This username is also used for log-in, along with your password.
On Mac, if you prefer to use it as a mounted volume, you can use the option “Mount Network Volume” on the Job tab sheet to make sure the volume is mounted.