I have been a Falun Dafa Practitioner for six years. I have to say that everything it discusses is real and genuinely upright. There are no rituals, membership, costs, and no worship. It discusses all aspects of cultivation in general (buddha, tao, qimen etc), and all of the info can be found for free on the internet. If you see what is really there, you will absoutely gain things you never knew existed.
As far as the previous comment, I question whether they are just repeating Chinese Communist Party propaganda. We only get together to do exercises. Also many practitioners protest the vicious persecution going on in china, but people together reporting on persecution can hardly be called a cult. It has been verified by the U.N., U.S. Congress, E.U. etc. The CCP outlawed the practice when a countrywide survey showed 100 million practitioners. they also outlawed other Qigong as well.
If you want proof, check this independent investigation out.
As far as the practice goes though, I have only found amazing things from it.