Did they give you a reason why you should take it in the morning? Some people who have trouble with side effects take it before bed, so they can sleep through the worst of it.
I was less than impressed with Imuran at first, too. I've been on it for about 10 weeks now, and I'm finally starting to feel better. It just takes a while to work it's way into your system. My original GI took me of Pred too soon, and the Imuran wasn't up to speed yet, so I was feeling pretty rough for a while. My new GI got me back on Pred and doubled my Imuran- I had only been on 50mg/day- and now that the Imuran is starting to work we're going to taper off the Pred again. Maybe you need a little extra help while you wait for the Imuran to kick in.
Hope things get better for you soon.