Excellent film. Have seen it dozens of times. Writing, directing, acting, cinematography, locations, sets, effects and message are top notch. I love the soundtrack (by John Corigliano), and often listen to "Second Hallucination" for pleasure.
Dr. Jessup has (along with other mad scientists) been my role model since I was an adolescent. And psychedelics are a valid means for improving the mind, when done SAFELY, and NOT just as entertainment.