I've used LSD in the 1mg+ range probably ~50 times? Highest was estimated to be 15+/-a few milligrams. Keep in mind, I'm speaking on milligrams here, not micrograms. Also used it in high dosages in the presence of MAOIs, and countless other drugs before.
Do you have specific questions about high doses of LSD on their own, or when mixed with certain things? It's such a broad question to just ask how the experiences are, in fact I don't know if any drug I've ever touched has managed to create more divergent experiences, honestly. Running into a lysergahuasca succubus in sleep paralysis is far separated from watching a book fly around like a bird, then become a biblical angel for no reason at all. How does that compare to seeing my reflection in the mirror walk away, nor to the colorful circus behind my eyes of whirring wheels and interconnected gears and catapults and the sort. Drinking a vial knocked me out in a ~4 hour DMT breakthrough according to my memory, but I was in fact awake, attempting to spontaneously jack off where I was (thankfully just in my living room) and asking my fiance stupid shit about if I could hypothetically ejaculate PCP. I was allegedly rolling around like a worm, slinking throughout the apartment and shit. All of these are experiences above 500ug, as I said, it's kind of a broad question to ask.