i had it once and it was pretty extraordinary. have had trips before, no other psychedelics.
didnt have too much for my first go.
was very peaceful - when i opened my eyes it felt like i was dead, but it was not bad at all. couldnt feel my body, and when i shut my eyes it was like i was in a dark forest with a weird gregorian chant (which was actually some constrction work going on nearby i foundout after) and some crickets.
some people have had scary alien experiences on high does (e.g. being anally raped by a reptilian alien - as read in dmt: the spirit molecule).
they say you shouldn't try it if you're not ready to die, because you will most likely think you are dead.