I was concerned about many things, and felt several doctrines were wrong or in need of change (including the creationism, blood doctrine and much of the 1914 doctrine well -- before I got on line and started researching JW history and while I was an elder). What did it for me was the "generation" change. At that point (late 1995) it was driven home that the whole religion was based on human guess work and had nothing to do with progressive understanding of scripture. Six months later I was deep in to discovering the amazing amount of information on the Internet and by April 1997 I decided to quit the religion completely.
Thirdson