When the NBOMEs came around to where I could reach them, I found that it was like a vacation from usual tripping. As stalepixel mentioned above, I found the experiences to be lacking in spiritual value or transformative potential, to be stimulating and merely impressive, not awe-inspiring.
They have the "weird body feeling" associated with 2C chemicals, but it only really manifests itself at high (greater than 1mg) doses, generally leading to a consesus that they have a "clean" feeling to them, as compared to the DOx chemicals that used to be widely distributed on blotter. There is a kind of emotional magic that occurs, and the time dilation is very impressive.
However, I am aware of the imprinting potential of psycheelics, and having taken 25I about 3 times and 25C around 10-15 times, I became aware that there are negative effects on memory. I have a hard time remembering most of the times I took 25C, and I was aware of severe rapid memory loss on 25I thanks to having a setup of 2 experienced trippers on the compound and 1 experienced tripper sitting/observing the session.
The observer said the people on the 25I would cognitively reach a revelation and emotionally soar with the joy that came with it, then he would observe a blank look as the cognitive awareness of the revelation was lost immediately while the emotional awareness/reaction would continue for about 30 seconds after the memory-loss event. And this was a pattern that recurred throughout the most intense hours of the trip. He went as far as to test it, with the overall dialogue structure emerging:
Tripper1: "Ah, I realize that I can blah blah blah!"
Tripper2: "Yes, I just realized that at the same time!"
Sitter: "So what is it that you just realized?"
Tripper1: "I....can't remember"
Tripper2: "Lost it already"
Sitter: "But I can see you're still riding the wave from it. You just said you realized you can blah blah blah"
Tripper2: "That doesn't ring a bell but it makes sense I think"
Blah blah blah being probably either nonsense or some actual revelation, and the dialogue taking place while still under the emotional influence of realizing whatever it is.
Anyway, this was an interesting look into 25I but for the very reasons detailed above I do not find NBOMe's to be exactly useful, and they may cause some kind of brain damage since they're so memory-lossy.
Also, there's this kind of laughing seizure that seems to take place, where everyone gets massive giggle-fits but the look in their eyes is not the pure joy it sounds like they are having, it's a sort of desperation, that they are trapped inside this prison of laughter.