I'm not on Imuran but I'm on 6-mercaptopurine, which is very similar. I am also on Remicade. So far, I haven't knocked myself completely into remission but I'm starting to have more good days and I hope that means soon I'll be out of this flare. Also, I haven't had any major side effects with either, just some fatigue, which I can't determine if it is due to the flare or the meds. My doctor also said that using the combination therapy has a higher success in inducing a remission and being able to stop steroids.
Best of luck!