The first time I tried 2C-I (26mg), I was fairly unimpressed. The second time (@25mg) I had a +4. The third time, I took 16mg and was amazed and how mind-expanding and lucid that level was. I then fell in love and 2C-I became a work horse. A clear-headed psychedelic with LSD-like analytical thoughts.
But after about the sixth or seventh time...I noted the headaches and the annoying stimulation it caused and eventually (when I discovered 2C-B, 2C-C, and 2C-D) I wrote off 2C-I.
Loved it, then it turned on me.