Honestly, just from personal experience, the profession seems to be marginally above chiropractors in legitimacy. Diagnosis and treatment is inconsistent and arbitrary - varying widely from practitioner to practitioner. Treatments are prescribed with "guess and check" methodologies. Longitudinal effects of many treatments aren't even known and results of many which have been eventually studied aren't good.
I recognize a lot of people have net positive experiences but the profession and pharmaceutical industry surrounding it 'needs improvement'.