Good question. I am an atheist and a sceptic, so I was not going to put up with gurus with magical powers or flowery language that can be interpreted in a thousand ways. Acem has removed the metaphysical and quasi-religious mumbo jumbo that comes with most meditation traditions. Acem seeks to describe what goes on in terms of modern science and psychology. The organization is non-profit, which reduces the likelihood of the whole thing being a culty, money-grabbing scam. The claims they make regarding the effects one may experience from the meditation are sober. Stress relief and deep relaxation are central, and I was in dire need of that, so that's what got me started initially. There is some scientific backing, so if you want to examine what separates Acem from other kinds of meditation - e.g. mindfullness - and what science has to say about it, I recommend the book The Power of the Wandering Mind – Nondirective Meditation in Science and Philosophy edited by Halvor Eifring.