I read a lot of the book No God but One by Nabeel Qureshi. He converted from Islam to Christianity and he has written two books on the subject. One book is more of his personal journey including dreams and leadings of God and the other is an argument against Islam and in favor of Christianity.
Qureshi is interesting in that he left Islam at a time when he says he still loved Islam and disliked Christianity. This seems a bit strange to me but that is what he reports. Qureshi states that in Islam, each person must bear his own sin and God judges us by weighing our good and bad deeds, p. 39. If there is no redeeming figure as in Christianity and if there is sin which God punishes and God weighs different sins differently, then at least some Muslims would tend to doubt their own “relationship” with God, I think.
How would a person know if and when his good deeds outweighed his bad ones, thereby entitling him to paradise and a happy relationship with God? In Islam, certain sins are heavier than others and certain good deeds more significant. Martyrdom and jihad and killing for the way of Allah outweigh a host of lesser sins, but not every Muslim chooses killing for Allah or relies upon that as a means of guaranteeing a good relationship with God.
It seems to me who has never been Muslim that some Muslims will have the risk of doubting whether or not God cares about him or will favor and help him. Of course, others also run that risk, but this risk seems stronger with a Muslim theology than several others.
Qureshi says that no longer believing Islam was the most painful decision of his life. At the time, Christianity had little or no appeal for him. He says he did not want to believe in Christianity at all and that his previous visits at churches left him not wanting to go. He says he had only 3 Christian friends and wondered how he would fit in, if at all.
Of separate interest, Qureshi is a pacifist, based on his understanding of the passages in Matthew. I assume that the writer of Matthew was a pacifist, that the writer of Luke was not and that the church figured things out gradually after Constantine.