Rather than straight cash, using it as a more-secure credit card would be enough to sign me up. It would prevent card skimmers, people copying numbers, etc. They could generate one-time card numbers for online purchases at existing merchants. Despite lots of mitigations, VISA/MC still have huge fraud problems. This would give them a new tool to lock things down.
Given that both VISA and Mastercard are on board, I assume that you might not have a choice in the long run.