Here is the real answer. Yes, it is a religion because it deals with the spirit, human soul or what ever you prefer to call it. Therefore is does not fall into any other category.
Some Scientologists believe in God, some don't. There are people of all different religions who also practice Scientology. In no part of Scientology does it tell what to believe or what not to believe, as far as God goes. It is a practical religion and it's practises work and are not based on faith, but on actual proven results. Scientology actually supports all religions and it is non-denominational.