This isn't a hard lesson to learn about AirPlay as such, more a lesson about network-dependant protocols in general. At the end of the day, if the network is solid then AirPlay, and any other network-dependant feature, will work. Unlike what the topic poster suggests, there isn't a 'fundamental problem' with the AirPlay software.
I had issues with my Virgin Media 'Super' Hub which caused WiFi to drop out, or computer-to-computer file transfers to stall or stop completely even with a full WiFi signal. It also seemed to stop issuing DCHP leases at will, which caused devices on the network to lose their IP addresses on a fairly regular basis, even those which were hard wired. AirPlay would also suffer under this setup.
Since I switched my super hub into dumb modem-mode only, I now use an Apple AirPort Express as my router which has provided a bomb-proof network so far. Coverage seems slightly less than the super hub, but even on 2 out of 4 bars the connection is solid, fast and reliable compared to the full-bar signal I got from the super-hub. AirPlay has been rock solid since.
The trick is to find a router that works well for you - it doesn't have to be a pricey Apple one (although I do recommend them), but anything is better than the terrible freebies that the ISP provides.