I watched Y&R for a good number of years. I remember when Jill gave birth to Phillip. I stopped watching and never returned during the "mystery" of who killed Dianne. It had become so horrible for far too long that I just had to stop. The reason I mention this is only so my thoughts on Billy Miller joining GH are perfectly clear. When I was in love with Y&R, and Billy Miller came onto my screen in a few minutes I would become aware of an unconscious gritting of my teeth.
I think GH has enough characters on canvas that it could do well without the addition of Billy Miller.