Here in Australia, we still have numerous retailers who don't accept credit cards or have minimum purchase amounts - due to, I presume, the cost of accepting credit and debit cards here.
I don't know whether costs are reduced for PayPass (tap to pay), but it seems anecdotally that any place supporting PayPass has removed credit card minimums.
I haven't carried cash in months due to PayPass (and discovering my debit card actually had it). I still don't like the "always on NFC" nature of it (I want a button on the card to turn it on), but it's quick and seems to go through a lot faster then the old PIN systems.
I've seen "offline approved" as a response from some of these terminals - I wonder if that means it's checked later?
PayPass is used by high volume merchants where the cost is low and absorbed. The retailers who have minimums on EFTPOS are using expensive PSTN units that cost up to a dollar per transaction.