I got mine done in Manila 2 years ago. (it is free when you are out of the country) Dropped it off in the morning, picked it up in the afternoon.
Mine is the older style, issued in 2002.
The original had numbered pages up to 24.
They added pages in the middle, lettered B thru X, between pages 12 and 13. It was stiched and taped. The A page is covered with an official looking notice stating the pages were added at the embassy, and it is embossed with a seal.
All my old pages stayed the same. I will be adding more pages before it expires in 2012.

I have been told that for the new style RFID passports you cannot add pages, but when you have it issued, you can request more pages than normal.