I've played with them. It feels like a hybrid of a Arduino that runs ladder code. Hardware feels cheap. The inputs are only protected with pull down resistors, no opto isolation. For some brilliant reason they do not have onboard voltage regulators to power off of 12-24vdc, instead you must power it with 5vdc. Out of the box it doesn't come with any of the required terminal blocks nor is it DIN rail mountable by default, that's another optional add-on.
I personally did not like the software at all. It seemed very clunky requiring a lot of mouse usage, then back to the keyboard, back to the mouse, etc etc. For all intents and purposes RS485 does not exist in their world and RS232 is limited to a few models (and I'm not sure it's even RS232, I suspect it's actually TTL level). Ethernet simply does not exist.
If you need a really, really cheap PLC with quite a lot of limitations, I guess they might be ok? Or if you need a lot of analog inputs in a very, very tiny form factor (they have a model that does 12 analog in, 0-10v or 0-20ma depending on what model you buy).
Past that, I can't see a reason to not use a Click from AD. The Click has proper onboard voltage regulation, expandable, RS232, ethernet or RS485 on higher end models, opto isolated inputs, etc.