I'm pretty new to the whole bootleg trading scene, and even newer to recording and editing stuff myself. I've tried to be as fair and objective with my quality ratings as possible. I shamelessly grabbed the ratings that other VOL traders had on their sites and typically rated my copies with the lowest of the ratings that I found. For shows that I couldn't find other people's ratings for, I tried to aim a bit low in my ratings. I welcome feedback on the ratings I've assigned to anything that I trade.
I plan on eventually comparing all my recordings and trying to normalize all the ratings to some sort of consistent scale, as time allows. Generally, I reserve A+ ratings for stuff that's nearly studio quality, like radio broadcasts. Shows in the B range would likely be enjoyable, but with clipping and other defects. Shows in the C range would be pretty bad, and anything below C wouldn't be worth owning. Again, if anybody has any wisdom to impart on how to rate shows, I'd love to hear it.