Two answers. Yes & No.
There are two types of Mesh networks.
Ad-hoc Mesh, in which devices come together, forms a network and traffic is routed from one device to another in p2p fashion. Users with their mobile devices are enough for this type of network.
Infrastructure Mesh, in which we need to create a wireless back-haul mesh among wireless routers and Access Points. Users with their mobile devices + wireless mesh infrastructure is required for this type of network.
It's easy to achieve ad-hoc mesh, since it doesn't require anything other than users and their devices, but these networks cannot replace the mainstream Internet which is hierarchical. So, Yes, we have tried ad-hoc mesh using Project Byzantium and we are already using Rumble (I am still confused whether rumble is just ad-hoc or it's a ad-hoc mesh).
Infrastructure mesh needs to be setup with routers and access points and that involves additional cost. And moreover not all routers can participate in the mesh network, we need to find the OpenWRT supported devices and flash with it or we could use a SOC like beaglebone / raspberry pi. Either way, without identifying proper mode of funding, we cannot proceed with this type of mesh. This would be time consuming, nevertheless this is what we need to push for. These infrastructure based mesh have the real potential to replace the existing hierarchical Internet thus eliminating the need for ISPs. So No, we haven't yet started working on infrastructure mesh networks.
Whatever type of mesh network it may be, we should remember that we also need applications that are also p2p to deploy on these networks. Though decentralized but not p2p applications will work on these networks too, but as more people join those services, they too will become centralized. For example, Diaspora can be hosted on a mesh network, there can be many pods, but if only one pod grows in number of users and the other pods fail to attract people, that will lead to centralization again.
P.S: I bought a wireless router from TP-Link exclusively for setting up a mesh node in my house. Before attempting to flash the router with OpenWRT, the router has got a manufacturing defect and I have submitted it for repair. When I receive the router, my first step would be to flash it with OpenWRT Image and install mesh protocols like olsr / batman-adv / cjdns.