I've been kind of intrigued by the Growtronix gear. I've done a lot of PLC work in the past, primarily with Allen-Bradley, Honeywell, and GE controllers. They are great for flexibility and reliability, but you need to understand that you are buying industrial quality gear and it comes with an industrial level price. I currently use an A-B MicroLogix microcontroller to run my stuff, but it is purely a localized digital controller with fixed I/O. I've been toying with the idea of integrating it with the Growtronix for SMS messaging, web interface, report functions, etc. Doing this kind of work on a PLC platform would be prohibitively expensive for what I do, but the Growtronix gear could be added for about the cost of a single interface board for most PLCs.