One rumor I heard (unsubstantiated) was that he will play the doctor who helps Ava recover from her burns...a new character, apparently. In typical soap fashion he'll probably end up being her new love interest, which...yawn...but the writers at GH seem to lack originality.
EDIT: shortly after posting this, I saw an article that stated (with pictures) that he will debut this week playing doctor to Samantha Morgan, not Ava, who is having some unique mental problems that has been causing her to say all the stuff we fans wish would be said about Alexis/Julian and Sonny.
As for the original topic, I have to say I was underwhelmed by Nora Buchanan's visit a few months ago. It just seemed to be a stunt with no real impact on the storyline, since any lawyer-character could have appeared. I sat there waiting for the other shoe to drop, some surprise that would justify the expense of having HBS appear, and...nothing.