3% Cash Back or 1%?

The Sun's Financial posted a list of credit card that earn cash back. The American Express and Costco TrueEarning card is the 3rd card on the list. The cash back percentage are indeed as Sun listed, I'd just like to add two things here:

1. 3% back of gasoline only for purchases made at Costco Gasoline and domestic stand-alone gas stations. Gas purchased at warehouse clubs other than Costco (for example, Sam's club), superstores or supermarkets WILL NOT count towards this 3%.
2. You will receive a 2% or 3% rebate only if the merchant submits the Charge for your purchase under the appropriate merchant code, industry code and required service or product identifier established by us (referring to American Express) and the merchant. If the merchant submits a Charge of purchase under a different merchant code, industry code and required service or product identifier, you will receive a rebate of only 1% instead of 2% and 3%. This change becomes effective on May 1, 2008. Note: I don't really quite understand what this is implying. Sounds like that we will depend on the merchant to get the 3% cash back, which will not be a good thing. Need to find out, and will update afterwards.