I started on Avonex 2 months ago, mainly because I liked the less frequent injections, although Avonex is an intramuscular injection where as the others are subcutaneous (in the layer of fat below the skin) so the Avonex shot itself hurts more cuz they use a bigger needle. After the shot I usually have mild fever and chills, some nausea and a bit of muscle aches. Taking Tylenol or Advil before and after the shot helps a lot. There hasn't really been any clinical trials comparing all of the different meds for MS, so no one can say which one is most effective, however you have less of a chance of developing antibodies (which make the med ineffective) with Avonex. Tysabri isn't yet available in the US, so us Americans dont have that option. Overall, I think I made the right choice, but I guess the side effects are different for everyone.