I personally found 600ug to be so disorienting and self-erasing, that I was never tempted to go above that dose. I strongly suspect that, at least in this subject, it would just result in amnesia and inability to process anything that is going on. That doesn't really appeal to me, hence I never found a compelling reason to do it. I would love to hear from anyone who went beyond this dosage range, and kept their shit together enough so as to be able to report on what is was like.
I find 600 to be the ideal recreational dose. 750 was much more disorienting but very rewarding. At 600 I was seeing an enormous amount of swirling neon runes/hieroglyphs, 3D spinning polygonal shapes, and experiencing synesthesia, but my sense of self was completely intact. At 750 everything was pixelated like the world was a Super Nintendo, everything was melting and rearranging, and my mind was producing rapid fire seemingly logical stream of consciousness thoughts and concepts. During the comeup I did find myself overwhelmed and incompetent, but it wore off and I was totally psyched for the rest of the trip.
AL-LAD to me is very logical and scientific, totally lacking the tricks and dark humor of shrooms. Even at 750 in the middle of the comeup I felt nothing malicious or sinister, just a barrage of data I couldn't process. So I feel pretty comfortable with the idea of pushing the dose further in the future.