I had some major reservations concerning the Orthodox view of Mary, including calling her the Theotokos. Then I went to an Orthodox service and saw her with Christ, and I noticed there wasn't a single icon of her without Christ also present in the icon. That's when it began to make sense to me.
She was the first faithful follower of Christ and in turn she continues to point the way.
As for the sinlessness and her body being assumed into Heaven...
She had the Eternal and Infinite within her womb, she said yes to this, so I have no reason to believe she would start telling God "no" after God had come forth from her womb! And as for her body being assumed, the way it's been explained to me is that Jesus is still Incarnate, so Mary is still His Mother. It makes sense that out of love for His Mother, she would be the first of the resurrected. I mean, what man doesn't love his mom?
But ultimately, I agree and disagree with the idea of Orthodoxy being more poetic. It is poetic, and it is mysterious, and it is only through participation we can see this...but after we have engaged in the mystery and the poetry, we begin to see the rationality. In other words, there is a rationality to it, but it's only accessible after you've begun to participate. I am still in the process of discovering this and only wish I had as much faith as everyone else on this board.