I'm in California, so mj is mostly legal now. I have not spoken with anyone who is HIV+, is in treatment for cancer, or who has glaucoma - or any other life-threatening physical illnesses - who is using medical mj. So for all I know it might be very helpful for those populations.

As for people with mental illness who have mj prescriptions, frankly, to me they don't seem any different than the stoners of old. In addition, their mental health does not seem at all improved by medical mj. Unfortunately, I'm not impressed so far.