Here's just one: Even talking about posthuman psychological superhealth is morally frivolous. Another? Promoting superhappiness may lead to what one may call, informally, "inappropriate" behavioural responses.
Accounts of use for depression, ADD/ADHD, fibromyalgia, chronic fatigue (off-label). Metabolic precursor to modafinil; takes 1 hr to kick in, hard on liver. Not "controlled" like modafinil/Provigil.