I filed my I-485 in September 2004, and was never called in for an interview. I got worried about that - but then found out from people in this forum and my congressman's office that some people don't get called for an interview if for one reason or another the case looks solid and they believ they can fast track the application without an interview. (...I came over on a K-1 fiance visa, so I had already submit proof of no criminal record, finanical stability, etc. before I was approved to enter the US - plus, I had already had an interview at the US embassy in my country before receiving the K-1 visa).
I haven't been approved yet - but just wanted to share that it does look like sometimes you can get approved without an interview. (And as far as "fast-tracking" - well, I don't think those two words exist at USCIS).