I just started my first remicade infusion last week, and I am on an Imuran + Remicade combo. I too asked my GI if it was dangerous. I told him that I read on a web page, that the combo was dangerous. He said that it was not a problem, so I left it at that. I have been on 150 mg of Imuran for about 5-6 months, and I haven't noticed much of an improvement, that is why I started on Remicade.
By the way, how long does it take to start noticing improvements from Remicade. I started on 40 mg of Prednisone the week before Remi just to get the inflamation down, and it has helped out a lot, but I was curious about the Remicade.