I have one, and so far it has been a little bit of a pain. The first batch went out with some faulty firmware that made setting it up all but impossible. However, as of last night, I have loaded the patch, and it is working very well.
The instructions leave a LOT to be desired, but hang with it, and it becomes very easy to program. I am sure if you order one now, you will get an updated firmware version and not have the same issues I did.
It is nice to be able to use 1 device for ATO, temp control, pH monitoring, lighting, and just about anything else that I can think of, and for less then $300 it really is a good deal. (A Ranco Temp controller is about $150, and a pH controller for my Ca reactor was about $120... so just the cost of those 2 items make up the total, then add my ATO, and it would have been cheaper to get the RK in the first place. (If it was ot then)).