Pam,
My Daughter has been on Imuran for several years now. Many Crohn's patients use Imuran or 6MP with very good results. I know that the side effects listed can sound scary. Most people really don't experience any, and do quite well on these.
The one thing to remember about Imuran is, it has to be at the peak therapeautic level to be effective. Usually, your GI will start you on a typical dose, like 100-150mgs per day. After a couple of months, you will need a metabolite test done to determine the level.
The only side effect I would be concerned about is pancreatitis. Some people do get it, but It will generally resolve in a week or so. It would mean that you wouldn't be able to take this drug though.