The percentile changed in the last month or so. On my official score report with an issue date of 8/23/06, 750-800 was considered 99th percentile and 740 was considered 98th percentile. On my official score report with an issue date of 9/28/06, 760-800 was 99th and 740-750 was 98th. I also noted that 700 is now 92nd, while a month ago it was 93rd.
I believe that the score is scaled based on exams taken within the last 3 years. It certainly does appear that the scoring scale is moving up at a rapid pace. It could also reflect some weakness in the test-taking group from just over 3 years ago (when MBA applications were extremely low) that are rolling off and no longer part of the weighting.