Interesting. I'm surprised he didn't get hardcore negative responses, despite the Shi'a/Sunni division.
The Shia\Sunni barrier is somewhat easier to break through. The essence- Quran, hadiths, sira, Muhammad the last Prophet remain the same-although many Sunnis believe that Shias aren't "real Muslims".
I think accepting "Ahmadiyyas" is going to be tougher-Muhammad as the"seal of the Prophets" is one of the essential doctrines of Islam.