NFC integration isn't just 'cool', it would be convenient.
I live in Oxford and regularly travel into London (a mere 45 minutes away on the train). If I don't wish to use cash, I will need to have two NFC cards (one, dubbed 'The Key' for Oxford buses, and then the Oyster card for London). And I still need to pay cash for my train ticket. It would be great if I could beep my PAYG Oyster at the start of my journey, and at the end, and have the cash taken off.
NFC integration, at least regionally, would make life a whole lot simpler. The London-centric south-east of England would do well to standardize all public transport on Oyster. Other regions where customers are less likely to have Oyster cards may wish to standardize on the nearest big city's transport NFC card.