I've been on Rebif since Sept 2009. I was terrified of the possible side effects.
So far, no problems, either with flu-like sfx, liver, etc.
You'll find lots of good tips here for how to inject easily, how to avoid the sfx, etc -- but here's my experience:
I take 2 Advil & 1 benadryl 30-45 minutes before I inject, and an additional Advil about an hour after.
I use a heating pad to warm the shot site for a few minutwes both before & after the shot.