I have been on one biologic or another (Enbrel, Humira, Simponi, and now Cimzia) since 2005. The only problem I have had is either local injection site pain, and eventual loss of effect (the reason I move on after time).
I have inflammatory arthritis with just the occasional pouchitis that has not been too bad. I was put on biologics for the arthritis and I have been very happy.
Just recently some pretty serious pouchitis was found. I was already in the process of switching from Simponi to Cimzia when I had my scope. I had been having a lot of abdominal pain, along with pouchitis symptoms. I'm on Flagyl right now for a couple of weeks and hope the Cimzia kicks in soon. If not, my GI advocates adding an immune modulator such as Imuran or methotrexate (already taking sulfasalazine).
To get back to your question, I have more fear of chronic inflammation leading to dysplasia and/or carcinoma than I do about the rare side effects of the biologics. I have my blood counts, liver and kidney function tests every three months like clockwork, and my numbers have only improved over the years. Prior to starting biologics I had mild fatty liver disease and my enzymes are now normal. Self injection was never an issue for me.
I avoid contact with sick people when possible, wash my hands raw, and stay up to date on my vaccines.
I am grateful biologics exist (and they are covered by my insurance)!
Jan