Well, that was a hard time for him, and for most of all.
I always thought it affected the singing...for example, YOU ARE MY LIFE, BEAUTIFUL GIRL, ONE MORE TIME, the way of singing these songs, for me, was affected by the problem. Check how his speaking was affected, by watching this video:
http://www.youtube.com/watch?v=EzGCZUT9DG4
It's really sad to watch him on the MSG show, he clearly didn't want to be there, it must have been really difficult, like the times when he had pimples and didn't want to perform or be seen. But anyway, I don't think it was just the lip, his nose was not in the best shape, his eyes were incredibly big, lifeless, the hair was a mess, those were hard times.
Ironically, he regained the smile by the trial period...leaving aside the situation, his best looks on this decade, were during the trial. He looked so confident, I never doubted him, but to watch him go inside the court house on that beautiful white suit, totally secure of himself...made just wanna kill anybody who said he wasn't innocent.