what makes anyone want to use a product that released a alpha/beta? If its good.
How else would they be getting it right without actual customers using the server.
The staggering local network effect required for mobile payments of this kind to be good require many people to use it right away. If nobody wants to pay with it, then no stores will support it. If no stores support it, nobody will want to pay with it.
This isn't some web app where you can get a few initial users off an HN or TechCrunch spike and then grow from there. It's completely useless unless a lot of people in the same area want to use it, in which case retailers will be incentivized to support it. If you want to do a limited alpha rollout, convince every store within 3 miles of 1600 Amphitheatre Parkway to carry it and give out free phones with Google Wallet enabled to 5,000 people in the area. Work out the bugs, then make a concerted effort to get everyone in the Bay Area using it. From there you can do a general rollout with support for every major credit card and national bank, plus deals with the 50 largest retailers in the country.
The level of clout needed to pull this off successfully makes Google perfectly positioned to do so. Their insistence on rolling it out as if it were a web startup all but ensures its failure.
Google's not under any pressure to ship. They should have taken the time to get it right before they pushed it out the door.