Paying attention is a requirement to driving, AP or not.
That being said, its not for everyone. Some people aren't ready to give up control of driving to a computer. Wondering constantly if the car will behave or kill you wouldn't be a good experience.
To this point, I feel AP has behaved nearly flawlessly. Its asked me to take over 1 time, when the paint on the road disappeared. Its made one swerve during an automatic lane change back to the initial lane. Overall those are acceptable to me in the approximately 1500-1800 miles of AP driving to date. Its priceless in stop and go traffic, and divided highways. Its a bit scary on undivided 2 lane highways, simply because a .1 second failure might end in a high speed head on collision. Therefore I only use it where I feel safe doing so. Its not for every situation either.