Just wanted to let you know about my friends who completed their interviews and got their citizeships.
My friend and his wife filed their N-400 applications on May 31, 2007 (Note date is June 5, 2007 for both him and his wife). They completed their citizenship interview in Baltimore, MD on Feb 7, 2008. They got their oath and received their US citizenship certificates on the same day of the interview. Their intervew went very smooth. so it took 7-8 months for them to complete the road to their citizenships. The interviewers asked them for tax returns and certificate marriage. They both answered their 6 history questions and wrote one sentence. By the way, they were interviewed separately.
I am waiting in my turn for interview since I sent my N-400 on December 18, 2007 (Notice date: Jan 8, 2008). I am also in Maryland.