Did you go to Mecca after you became a disbeliever?
No, but I pretended to be a Muslim for many months before I came out to my parents, (praying at the mosque every evening, going to Islamic talks occasionally, and in Ramadhan 2008, I fasted, prayed Taraweeh and payed Zakat as a closed atheist).
The thing that struck me most (and it's nothing new) is the sheer lack of questioning in Islam. Everyone just conforms blindly (for survival, I guess!). I saw (orthodox) Islam as a cult that can only survive under certain conditions, i.e. isolation from outside influence, both real life influence and via the internet, TV, newspapers, magazines, books etc.
Religion also takes advantage of various cognitive biases that we humans are prone to, and I was thinking about these too.