The following steps will help you avoiding issues with duplicates during a first-time installation of fruux:

• Choose the Mac that contains your up2date data
• Backup your Addressbook data, iCal data and Safari Bookmarks (just in case)
• Download fruux
• Doubleclick the file fruux.prefPane and install "Just for the local User" (NOT "For All Users")
  (make sure that the filename is fruux.PrefPane, otherwise you might end up with issues when updating fruux in the future)
• after some seconds fruux opens
• Choose the "New User" Tab, enter your emailaddress, choose a password and enter it again in order to confirm it
  (make sure that you entered your emailaddress correctly!)
• Click "Save Changes"
• After some minutes you'll recieve your confirmation email
• Click the link in your confirmation email in order to activate your account
• Click "Synchronize Now" in fruux
• After some seconds you'll see the status "Sync OK"
• Activate "Always keep synchronized"

You sucessfully signed up with fruux and synced your first system with the cloud. Now let's prepare your second Mac for fruux:

• Delete your Addressbook contacts, iCal calendars, and Safari bookmarks
  (If you already installed fruux on the second system, disable "Always keeps synchronized", otherwise your delete will be synced with the cloud and thus wipe your data in the cloud and on your other systems, too!)
• Download fruux
• Doubleclick the fruux.prefPane
  (make sure that the filename is fruux.PrefPane, otherwise you might end up with issues when updating fruux in the future)
• after some seconds fruux opens
• Choose the "Existing User" Tab and enter the account data you used on your other Mac
• Open the "Revert" Tab
• Click "Reset this computer"
• After some seconds you'll see the status "Sync OK"
• Activate "Always keep synchronized"