I saw the first preview. I wouldn't call the play "bad", so much as wrong headed. The only play of Shawn's that I had seen before was The Designated Mourner at the Public, and there i found his writing very impressive. Here he creates what seems like a realistic situation, and then goes off in different directions.
There are some strong moments in the writing: a monologue for the young woman in the play, and a memory of the character that Shawn plays talking about wanting a role that he did not get. I thought that Broderick gave it his all---he has a very long role; did not find him boring, he plays a kind of intellectual person who discovers a lot during the evening and I thought he took the journey well. But there are a lot of contradictions in the text---the major revelation about people's behavior just seems odd and strange. The cast is really strong---it was great to watch Jill Eikenberry and Michael Tucker in the play, but their roles are sadly under written. If you find Shawn interesting as a playwright, there is at least a lot to consider here. But you have to be prepared to go with the vision.