My initial thoughts are that if you've owned a truck and don't know if you need 4X4 you probably don't.
The above said, not only does a four wheel drive system help prevent you from getting stuck, and get going in slick conditions, it more importantly gives you much better control than what you get with two wheel drive. Unfortunately, with some vehicles like my new Ram 3500 the torque management takes away some of that control as you don't have the fine throttle control you need in slick conditions.
The above said, you can, and I often do get stuck even with 4 wheel drive. I go t stuck in my last truck 3 times in the last two years, but only once with the trailer hooked up and that was in a place where sand had drifted across the dirt road I was on.