i received an identical notice in connection with my amex Clear, it notes several apr increases. None pertain to regular purchases at this point.
I had a similar message regarding my Optima Platinum: No increase in APR for purchases.
According to Experian, AMEX requested my credit report (for Account Review) on 4/21/2007, and not again until 11/12/2008. I only use my card 3 or 4 times a year. I pay my balance in full the day my purchase transaction posts. Also, my Experian score has been 830+ for the past 2 years.