These are comparable to the internet: they are relatively easy to set up, and are inexpensive, autonomous, reliable and resilient. Think of them as a scale-down, local version of the Internet.
WiFi and Wireless Mesh operate differently, and are not interchangeable. Wireless Mesh technology also differs from WiFi hotspots in that - in many cases - local councils or administrations, rather than private companies, set up the meshes. As such, they are geared towards using the community rather than producing good-looking figures for the balance sheet.
The purchased report compares 27 US-based LAN wireless mesh network products. This report highlights the benefits such a venture can bring in high density, relatively close agglomeration, although citywide coverage would be problematic.
Like Peer to Peer, Mesh networks actually depend on sharing resources in order to work effectively. There are literally hundreds of grass-root led organisations around the world that maintain independent meshes accessible by anyone with a wireless connection.
Needless to say, something like Bittorrent, which almost coerce the user to give as much as s/he receives, would be more than welcomed. However, Bandwidth heavy Bittorrent will not be the ideal application for low-cost, low-bandwidth mesh networks.
Wireless Mesh Networks will only pick up if hardware vendors make connectivity as cheap as chips; unfortunately that is not happening any time soon.