They can be very bad for some. I have never had a bad experience. It's how you handle it. Some just can't handle it very well. Those are usually the people who are weak minded to begin with. When I did acid it was always so fun....you really do start to look at the world differently...and I still do because of it. Makes you realize most people aren't really who they appear to be.
For some strange reason I had super hearing when tripping. Maybe I was just reading lips, but I swear if I looked at someone, no matter how far away they were I could hear the whole conversation they were having, like I was there having it with them. You do get a really big body buzz and I did see thing. Not things that didn't exist. Just things that would modify. Either shift or melt or sway. I actually felt like I could think clearer while on acid. Most people never know I was on it, except my pupils would enlarge to wherre you had no color in your eye.
Tripped balls at my HS prom. I thought I was an FBI agent in the X-Files and almost cracked this kids skull with a pool stick as he just put off a bad vibe. Had a good time though.
Also tripped at Island of Adventure once(theme park in Orlando)...now that was an interesting experience. Being around all those people and going on the rides. Wow...what a time we had.