I dropped our I-751 (application for removal of conditions) in the mailbox on 9/10. Yesterday, 9/23 we received an I-797C from INS in the mail acknowledging receipt of our application and extending my wife's green card for one year while the application is processed. The 797 states that it normally takes 120 days to process an I-751 and to notify them if we've heard nothing after 6 months.
That's less than two weeks from mailbox to mailbox. I'm happy. I would have thought about 3 days in the mail each way and maybe two or three weeks for the paperwork to progress through the data entry queue and acknowledgement processing.
Incidently, I sent the application to Texas. They have their own web site guiding everything, including how they would like you to label cover letters and envelopes. I recommend following their instructions, regardless of what any other helpful contributor puts on a web site. In the case of Doc Steen's site, Immigration attorney Matt Udall has issues with its currency.
The Texas INS web site:
http://www.ins.usdoj.gov/graphics/fieldoffices/texas/aboutus.htm
