There are not one hundred people in the United States who hate The Catholic Church, but there are millions who hate what they wrongly perceive the Catholic Church to be.The above quote is from Archbishop Fulton Sheen, and I've found it to be fairly accurate, at least in my own experience. I was raised Southern Baptist, but converted to Catholicism in 2004. Here are some of the more common misconceptions I've encountered, either in my own understanding or in others.
-Purgatory. This is a pretty big one, really. The usual misconceptions are that purgatory is some kind of "second chance" and/or that it negates Jesus' sacrifice and instead focuses on earning your way to Heaven. In fact, neither of these are true. I mentioned that I was raised Southern Baptist, in a congregation that taught "once saved, always saved"; if asked what would happen to the person who still held on to some sin at death, some would answer that those sins, or any attachment to sin, would be immediately burned away and cleansed upon death. Well, that's essentially purgatory. We don't know how long it may take for this cleansing, but it could be in the blink of an eye. This doesn't negate Jesus' sacrifice, but is the application of His sacrifice after our death for those of us who die while still in some attachment to venial sin. It's a great act of mercy from God to cleanse us in this way so we can enter Heaven.
-Faith/Works. Purgatory leads to me the discussion on faith and works. Many seem to think that Catholics believe they can earn their way to Heaven through various works. In fact, Church teachings are very clear that salvation is by grace alone, through faith and works. This doesn't mean that we earn our way, but it does mean that we can't just say we believe and then not live it out. After all, St James tells us that faith without works is dead. The parable of the sheep and goats makes it clear that our actions matter. Again, this doesn't mean that we earn our salvation - it is only by the grace of God, and He also gives us the grace to perform these actions.
There are many more, but I'll stop with just those for now. :-)