If you think of it as its being pitched ~ the Linux/Liminio side that can do the networking ~ then it becomes really powerful, and only the web interfacing becomes the programmable area.
This can be into the internet - or if WiFi supports 802.11s - Mesh Networking - then there is a mesh networking.
Also, what might really work is being able to do an HTTP based UI - if a decent java script server can be got running on the YUNs web page.
Another way of doing the same thing - a Arduino board with USB to an OpenWRT device - eg Netgear WNR3500L - its about the same thing.
So instead http://rayshobby.net/
Atmega328 (or Pi) irrigation controller, it can be relays off a YUN with wireless or wired networking whatever is available, and a more sophisticated mash up of weather information.
The Maker 2013 in San Mateo did show a limitation of WiFi - there was so many SIDs broadcasting - none of them could work .