YESSSSS!!!
A little while ago, I posted a thread about receiving a 25,000 MR offer in the mail for an Amex EveryDay less than a month after being approved for an EveryDay (with a 15,000 MR offer) and asking everyone if AMEX would match the sign up bonus they sent me by mail. Most posters said that AMEX is not really known for matching sign-up bonuses and that it would likely be a no. I called Amex, and two weeks went by without any answer. I called again about an update, and sure enough, a few hours later I received a message saying -- more or less -- "We have investigated and confirmed that you received a better offer than the one you applied for by mail, but we are not going to match it." I said to myself, "Well, darn!" and thought that was the end of it.
Well, today I log in to my Amex account and see I have 10000 more MR points than yesterday, and after going to the points summary page, I see that Amex decided to match the offer after all! Yahoo!!!! Thank you, AMEX! 
Very rare indeed
I once got a better offer via mail 3 hours after I applied and was approved
They shot me down twice to match that offer 
So kudo to you 
Sounds like you got lucky! Congrats! 
