I filed I-751 at TSC last Nov, and had Bio done Dec. 2006. I haven't heard anything since then. Called 1-800 number on Aug this year, and got a letter saying additonal time needs to process the case in about 45 days after I called. Online status showed last update 12/29/06, and status never changed since the beginning. I am eligible to file N-400 now, and I think I will file it next week. Please keep me posted of your update if you are in the similar situation.
Thanks.
Bitter_melon
I was sweet patato before, but after my case out of processing time for couple months, I am truning bitter and bitter.