Like I said - if one were to binge on incapacitating doses for even a couple of days, and one will find, in the days during and afterward in one's self-perception proof for the studies cited by Blowmonkey. We knew that heavy K-use carried all these risks before some cute little psychiatrist decided to "discover" them. We also have always known of the miraculously beneficial effects. It is only a matter of time before some discerning scientist decides to "discover" them, too.
Taking ULD and having some patience (usually within a day after 1st dose), seems to consistently allow people to come upon a sudden, unique, and impossible-to-miss effect that is characterized by a sense of restored-balance (emotional, mental, and even bodily) along with clarity of thought, improved memory recall, and enhanced eloquence. It is also very distinct from the euphoria experienced on recreational doses, as well as being different from the well-reported "afterglow".
I was able to observe "duplicate results" (so to speak) of this effect in every single person who tried a ULD course (adapted to their own bodies - main variables being exact dose, frequency and route of admin.) and stuck with it, then got back to me with the results.
Also those who tried and got good results then succumbed to bingeing on recreational doses (myself included in a couple instances) found, invariably, that said binges destroy most of the beneficial effects and add their well-known risks. (by "invariably" I mean specifically the 20 - 30 people who gave me feedback over the years).
To re-emphasize: I am in no way saying that bingeing on recreational doses of K is devoid of risks - it most definitely has its risks, both mental and physical. What I am saying though is that in my and several others' personal experiences, a ULD (12mg in my case) regimen appears to act as an entirely different drug.
And of course, the golden rule still applies: YMMV.