Brother Sunnis do take Shias as Muslims though seriously disagree with and detest some of their beliefs and practices - the Proof being that Shias are allowed to visit the holy places for thier rituals unhindered.
About the posters - that refers to extremists beliefs within Shias - those who make takfir on the Companions of the Prophet (saw) [may Allah be pleased with them all]
As far as your question about the Ayatullhas is concerned, in my opinion, if they accept followers of Sunni madhab as Muslims then they recognize the madhabs.
That's not true brother - Ayatullahs accepting Sunnis as Muslims doesn't mean that they are accepting Sunni schools of thought as correct - they don't.
The Shia/Sunni differences and disputes will only be solved by Imam Mahdi (ra) when he comes. Till then bear each other out.
Eid Mubarak to you and all the readers here