Most religions tend to promote their doctrines on the basis of the claim that they are "true" (it's true that God exists, the Jesus died and rose from the dead, that Muhammad was the prophet of God, etc.), but Scientology usually focuses more on the claim that it "works." Of course, something that works may sound like it must also be true, but something that is false might appear to work if you don't really understand what's going on. That seems to be the case with Scientology.
In New York City, many of the firefighters who worked in the ruins of the World Trade Center sought relief and emotional counseling in a medical clinic that was really a Scientology group peddling pseudoscience about mental and physical health. Scientology's entire "detoxification" program is unsupported by objective, peer-reviewed medical evidence, so apologists tried to claim that it would be "unfair" to wait until the evidence came in.
Of course, it's only "unfair" if the treatments work, not if they are pseudoscience, and that's why we need to evidence in order to find out. Scientology wants to be considered a religion, but when it comes to getting others to apply their beliefs, they want it to be a science instead. They can't have it both ways. If they want to be treated as a religion, they should stick to that; if they want to be treated as a scientific organization, they should stick to that instead.
They'd be better off with the former, though because it's false that Scientology "works" - it doesn't "work" any more than the Bible, the Qur'an, or any other religious text that has been written over the millennia. Scientologists have faith, but what they don't have is science. Despite constant claims that their religion is "scientific," they can't provide any peer-reviewed, scientific data that would lend the least bit of legitimacy to their religious faith. Scientologists who believe that their religion is scientific have been misled as to what science and the scientific method really are.
Scientology is no more scientific than Young Earth Creationism - and it's arguably worse, since at least creationists admit that there is a measure of faith in what they believe.