There are a lot of naive people on the site nowadays, i havnt been on for a few months and there are more and more threads where people are talking bollocks about drugs...what happened to the 420 forum?
Anyway, there isn't a ratio of good to bad mushroom trips, it all depends on the person's mindset before (and during) the trip. Certain foodstuffs can affect it, such as alcohol and caffiene (can increase length of trip) and it's generally best not to have them on a full stomach as it can upset your tummy.
Having done them twice, i know they are not for me as i can tend to be a little paranoid whilst trying something new. This caused me to have nightmarish trips, although it didnt help that on one occaision i had drank alcohol, eaten and drank redbull before hand. (for reference i took 40g of fresh columbian mushrooms, bought in Amsterdam. The other time i took 20g of fresh and it was not half as intense or lengthly. Anyway cut a long story short, they can't fuck u up unless you are mentally unstable, but u could have a bad trip. Or you could have a great trip. the end.