Just cancelled my IEC Centurion after nine years. Got a pro rata refund of my membership fee, and that was that.
When I joined, the membership was €2200 and due to the bonus, you earned 2 MR per euro for the first €100k. Due to frequent offers, this could mean 3 BA Miles (now Avios) or more per euro spent. In my mind this went a long way towards offsetting the eyewatering membership fee. I also got a lot of use out the Mandarin Oriental free night offers.
Fast forward to now, the 100K MR bonus is gone, the membership fee is €4000, and an euro spent earns two thirds of an Avios. The free night benefit is essentially gone. The only part of the current offering I'll actually miss is the Hilton Diamond status.
All that said, Centurion is quite clearly a luxury travel product and if that is your lifestyle, you can still extract plenty of value for the price. The suite upgrades I've received over the years have been nothing short of spectacular.
I switched to the locally offered Platinum card here in Finland. It earns more MR per euro than the Centurion, and the conversion ratio from MR to Avios is also better. Like most markets but unlike the IDC/IEC cards, there's also an Amex iPhone app. Local promotions and retail offers. And a prospect of Apple Pay down the road, something that doesn't seem likely to ever happen with the international cards.