As I said, I want to like the Iro... I just haven't swallowed the Kool Aid yet
I challenge the notion that more than 16 zones pus it into a "commercial" class. For example, I have a orchard that I water with a drip system. It has a mixture of citrus, avacado. To the Iro, these are "Trees" on "emitters" with "clay/loam" soil. However, the avacado has vastly different water demands than citrus, depending on time of year, ripeness of fruit, etc. No amount of "intelligence" in a single zone is going to be able to deal with this difference. A $25 trip to Home Depot and another valve and some wire solves the problem, all I need is another place to plug in the zone.
I have another lawn that is shaded by one set of trees in the spring and summer, and another later in the season. I have Tipuana shade trees that loose their leaves in February and regrow them in August, causing weird shade patterns on the same lawn. Calling this lawn "somewhat sunny" in the Iro ET algorithm and averaging out the water for the year is not going to solve the problem. Splitting the lawn into multiple zones (maybe 3) is the way to do it. But I need to add more zones to the controller.
So, greater granularity of my irrigation system seems to be a huge win, water wise. I'm not that excited about having the 10 parameters per zone when I don't have the zone control to do the watering.
The chances of all my valves, sprinklers, and drip emitters working as planned every time is pretty slim. I've had two pipe ruptures while on vacation that have cost me $2000 in water bills. There is a huge difference between putting numbers into a controller and what actually happens... this can only be understood by measuring the flow of water, which I understand is not on Rachio's horizon.
This is a bit like running your furnace by saying, "A panel of experts has determined the proper number of hours per day that you should run your furnace, based on very precise measurements of your lat/long/altitude, number of windows, insulation, number of people in the house, number of hours you run your oven." Our furnace controller also allows you to fine-tune these parameters with the latest intelligent software." Even the cheapest thermostat creates a closed loop control system, eliminating the need for expert heuristics and whatnot.
Iro runs open loop - we can argue about the futility of soil moisture sensors in a separate topic - so, without flow measurement feedback, it's like our furnace being run by a expert committee than adaptively by looking at what's happening.