Antimatter and Matter Energy Question?

I just finished reading a recent article on antimatter and I was wondering...The article stated that when matter and it's opposing antimatter came in contact with one another, they would both annihilate each other completely to produce energy. In saying this, does this conclude to the fact that this is the perfect example of pure energy production? Whereas, all the amount of matter is completely turned to energy? I'm very curious...any suggestions?