A small firm in suburban Missouri is building out a neighborhood at a time: Network 1 is building in bits and pieces, signing up customers as they go. This strategy might work. It's less capital intensive, although you still have the cost of building a network operation center and your backbone network; it's just that it can be built piecemeal. It also means that problems with technology or assumptions can be corrected as the network is built and as customers start using it.
I don't want to sound too optimistic: there are still plenty of technical, political, and financial obstacles in the way of having metro-scale Wi-Fi work. But I do think the days of 95-percent city buildout requirements led by municipalities that don't contribute any funding or buy any services are over. It's more likely that we'll see a combination of public space unwiring, business-grade point-to-multipoint broadband wireless, and something like reverse redlining: Wi-Fi brought to areas with high dial-up penetration and poor broadband availability, likely in lower-income parts of cities.
The company so far has just 150 customers and 10 square miles of service area--although it's unclear how fully unwired that coverage is. That's a pretty tiny number, and we now have to see if the network remains reliable and scales as users join.
The folks at Network 1 are using some kind of homebrew equipment, but the results so far seem fine. Tim Logan, the reporter at St. Louis Post-Dispatch who wrote the linked story, said the firm was playing it close to the vest as to what gear they were using, but that they were employing off-the-shelf equipment. I expect that RoamAD or LocustWorld is being used for the routing portion of their network.