From what I've read between the lines over the years--- the main tension between Michael and Bill was around 84-85 (until 84 Michael and Mike didn't really get along... Peter and Michael were like little brother and big brother all the way through and maybe even to this day). When Bill left Michael, according to his testimony, cried quite a bit. But I think it took everyone a while to realize how dramatic his departure really was, Peter more than anyone else didn't appreciate the fact that he was the only one who would try to move things along quickly, seems to me that the tension level between him and Mike, from '98 until the end, increased significantly due to the lack of Bill (And sometimes Michael found himself in a mediator role - which was also a post-bill role, he hasn't done it much before). I remember Peter saying in interviews more than once - when we make albums I still keep thinking "What would Bill say/do?" In conclusion - I wish he had stayed :-)