I have done all the above steps. I have a 2010 Macbook Pro running mountain Lion, My phone is running iOS6...
I have done everything according to the steps on this link: http://support.apple.com/kb/HT5372?viewlocale=en_US&locale=en_US
I am running Mountain Lion on a 2010 MacBook Pro and iOS 6 on an iPhone 4. The iCloud tabs button gives only the default "iCloud shows all the open tabs on your other devices".
I'm at a loss as what next could be done to get this feature functioning.
iPhone 4, iOS 6, iCloud syncing