I went for my originally scheduled appointment but it didn't work. Ended up being a big waste of time and money.
The details posted above by coredump are correct. My original appointment was at the 7880 Biscayne Blvd office. Security at the gate noticed that the appointment was for a citizenship interview and did not let me through because they no longer handle these at this office. An officer in the customer service center, which is next door, suggested I go to the citizenship center (77 5th St office) about 8 miles away in downtown. He sounded positive and said they would look at my case if they had my file. But at the center, they wouldn't let me in either. The guards told me that a lot of people had been rescheduled from the other office. They had no interest in listening to my case, the attitude was more of "shit happens .. letters are lost in the mail .. wait for letter" and so on.... The only way to get in was to fill an info pass form and talk to the information cell. But this was a Friday and they have stopped doing info-passes on Friday. The infopass website still says M-F but not really ... So no luck, had to go home. On Monday, I had to be in the area and I decided to take a chance and try an info pass again. After waiting for about an hr, I got to talk to the lady in charge. She was in a pretty bad mood because their computers were acting up and probably because the lady ahead of me had successfully aggravated her further. It took her (the computer actually) about 15 minutes to look up my records and confirm that the appointment had been rescheduled. She didn't know why I had received two interview letters. There was no way to do an interview on the same day. The center is very busy, they probably handle 300+ people a day, so its understandable that they won't take people on a walk-in basis.
If you are in a small DO, your luck may be different and it doesn't hurt to try. There was a guy in the queue with me who had also been rescheduled but had not received a new date. Don't know what happened to him but I doubt he had any luck. There was a lady who passed her interview successfully 4 months ago but no oath yet. And there was a guy who had applied in 2006 and had yet to receive an interview letter. The only people they seemed ok with walk-ins were those who had been asked to come back with additional papers.
Honestly, just be thankful that your delay is only two weeks and not more. This is a government office you are dealing with with all the bureaucracy that comes with it.