I use CDC for the cashback card mostly, for trading I was always put off by their withdrawal fees and the fact that they were less competitive than other exchanges. In my experience as well CDC disproportionally favor the most wealthy customer, most offers/bonus'/ways to earn have you needing to fork up quite a bit to be able to get any decent return.

That said the cashback card for me has been great, I have the ruby so it 2% back on pretty much everything which is not to be sniffed at and stacks up quickly. It is also really handy for travel as there are no additional changes for using the card in other currencies.