I just cancelled my Amex Platinum card and I feel so good! I will never need to worry about spending based on coupon book categories to "earn" back my annual fee or to get the most value out of the card again. I will once again spend whenever and however I want.
To be fair, I managed to get more value from the card than its annual fees in the past two years, however, it has just become too much a hassle for me. (I still keep other credit cards.)

Other people may find it more valuable than me based on life style but it is clearly not for me. On the other hand, I am sure there are also people who feel the same way as I do.