I am now on 6-MP. The side effects aren't bad-- I did experience a bit of shedding but I increased my folic acid intake and the shedding is even. No one noticed but me. I just noticed a bit more of my hair in the drain of the tub and a bit more on the floor of my bathroom. It does take 6-MP a few months to be effective.
I should note that I was first diagnosed with UC in the early '90's. I had surgery --complete removal of my colon and rectum and have a J pouch. My Crohn's is in my pouch. At first, doctors thought it was just chronic pouchitis but ruled that out as I have strictures, ulcerations, etc.