My personal timeline
Married in Dec, 2001
Get EAD in July, 2002
Interviewed in Jan,2003 and get Conditional GC, which expired in Jan. 2005
Divorce finalized in Sept, 2004
Filed I-751 in Nov. 2004
Received Notice of Action in Dec. 2004, and extension of my Conditional GC to Nov, 2005
Received interview letter for I-751 in July, 2005
I-751 Interview by myself in Aug, 2005
Two weeks later after interview, I received the permanent GC (10-year card) in mail(California service center). Hope this could be helpful for someone else, especially for those in unhappy marriage.