Set up my non-contactless credit card today and used it in M&S to buy my lunch.
Observations:
1 - Too slow. Ok in a shop, no good as an Oyster replacement.
2 - I just used my credit card to buy my lunch which is of course pointless. I could add my debit card as well but then I'd have to faff about selecting it, and frankly it's quicker to just pick the right card out of my wallet. Ok, I could set my debit card as the default but then I don't really gain anything over just using the contactless card.
I think where it will be good with my credit card is for in-app purchases.
HOWEVER - I don't know if this has been answered of not, but are you still covered by Section-75 card protection if you use this? Or is it like if you use PayPal linked to your credit card you aren't covered?