M had stomach pain and weight loss BUT she was on it right before being diagnosed with Crohn's. At the time, we blamed the Arava and switched her back to MTX, but she was diagnosed with Crohn's right after that, so we don't really know what was the Crohn's and what was the Arava. It was working really, really well for her joints - in fact, we may try it again.
My older daughter had diarrhea, nausea, weight loss, hair loss and fatigue with Arava. She had kind of an extreme reaction to it. She was on Arava for 3 months or so before we decided MTX was more effective for her and had fewer side effects.
Neither had issues with their WBC but they never do.
Good luck!