I can kind of sum up that information...
I've only used GW a few times but I think Wallet can automatically debit the account you have tied to Wallet. If this is the case, then those guys are clueless about Wallet (and I think they are...as they are not sure). BTW - Softcard can automatically debit any debit card (back up) so no balance is needed on Serve).
The person who said vendors needs to be brought on board hit the nail on the head and is 100% correct. Google never bothered to do this and that is why Wallet failed (blocking the app did not help though). To qualify that... even now that Wallet is unblocked it's still going no where as Google is still doing nothing with it. Getting vendors on board has always been the issue and ISIS's model addressed that issue. ISIS did it right... at least starting out. It's kind of like, "build it and they will come". Set up an infrastructure and people will use tap to pay. Advertising is not the big issue. With the introduction of Apple Pay more and more vendors will look at installing tap to pay. What we are seeing now is any upgraded payment device will simple accept tap to pay as they need to be some what future proof.
The other biggest issue and this is BIG.... tap to pay NEEDS TO WORK! I've been using ISIS since 10/2013. Even today tap to pay won't work 90% of the time. People are not going to use it is it does not work like a credit card. McDonalds is the exception. Every time I've used it there, it's worked.