I find the best use of AMEX MR is usually gift cards for the various stores that are in the program. You typically get $100 for 10,000 points(1 cent per point). Using MR for other items usually has a lower value - especially for redeeming merchandise and air travel....
Not sure I follow ... Other than the little annoyance that US tickets booked through AmEx (whether paid for by MR points or otherwise) cost $7 more, aren't you getting one cent of airfare for each MR point spent?