Though I am now an atheist, what initially woke me up were certain mystical experiences I had as an adolescent that simply did not fit within Watchtower theology. Of course my mom and the elders thought I was demon-possessed, but after reading Evelyn Underhill's excellent survey of mysticism I realized that there was nothing demonic or even particularly 'mystical' about what I was experiencing. Eventually I realized that the traditional religious explanation for these altered states of consciousness was just a lot of unnecessary baggage that created more questions than it answered.
Oh, and there's also the fact that WT theology doesn't hold up to any serious scrutiny and that the Bible is a mass of historical and theological contradictions. The GB should really consider forbidding JWs from reading the Bible or even any WT literature that is more than a decade old.