Any application that inherently needs more than one computer, due to its processing or physical layout requirements, could likely benefit from Qnet.
For example, you can apply Qnet networking successfully in many industrial-automation applications (e.g. a fabrication plant, with computers scattered around). From an application standpoint, Qnet provides an efficient form of distributed computing where all computers look like one big computer because Qnet extends the fundamental Neutrino message passing across all the computers.
Another useful application is in the telecom space, where you need to implement large routers that have several processors. From an architectural standpoint, these routers generally have some interface cards and a central processor that runs a set of server processes. Each interface card, in turn, has a processor that runs another set of interface (e.g. client) processes. These client processes communicate via Qnet using Neutrino message passing with the server processes on the central processor, as if they were all running on the same processor. The scalability of Qnet allows more and more interface cards to be plugged into the router, without any code changes required to the application.