We use the AmerEx rewards to cover the cost of the rental car at National Car Rental every time we go to WDW.
I think it is a great deal.
We use the DC to get a discount on the rental rate, then use the AmerEx vouchers to pay for the rental. The voucher can not be used to cover the tax, so that we do have to pay.
I had one gentleman from AmerEx Rewards give me a hard time about using the DC discount and vouchers together. This was after I had already done this like 4 times with no issues. At first he would not issue the voucher until I told National Car Rental I was using the voucher. I called National, and they kinda just said "yea, whatever" and still gave me the discount.
It works out that for every 1,000 pts you get $10 rental voucher.
Last June we got a full size car for about $360 plus tax etc. for 12 days. So we used 35000 pts to cover the $350.
I think it is a good rate. It fairs out about the same if you converted the pts to airline pts.
Sometimes we will convert the AmerEx pts to Continental pts and it is one for one. And if booked early enough and at off peak we can get a flight for 25000 pts, where as the flight usually costs between $250 and $300.
We have never used the "Be Our Guest" traveler's cheques, but I have heard they are not as good a value.