Thanks for sharing your experience. I would concur and my experience is similar with my Rachio controller. The first year was a bit rocky. This second year has been much better. Like you, it takes a bit of tweaking to get your particular situation right, but once the 'sweet spot' is determined, I've found my controller to be pretty much spot on. And, like you, I still have to water some 'trouble spots' by hand when it gets really hot and dry. Let's face it, even irrigation zones, no matter how carefully laid out, have 'micro-climates.'
Part of the difficulty I deal with is the irrigation system that I inherited with this home is set up with zones that don't totally conform to the types plants the zone waters or the sun/shade situation they are in. I have to strike a balance. Also, my back yard, even though it is in mostly shade, has some huge trees that really suck up the moisture from the soil. Consequently, I have to set that zone as “Lots of Sun” even thought it's mostly in shade.
Tweaking the crop coefficient and the allowed depletion have allowed me to have things watered at the appropriate times and amounts. Additionally, even though my front lawn is fairly level and I have the controller set for “clay soil”, I've also put it on “steep” terrain and “Smart Cycle” so I don't get run off. Now irrigation is done more efficiently. There is definitely a learning curve to get things set up right and where you want them, but once that is achieved, the system works pretty much flawlessly.
I can't vouch for water savings as my old system never kept things watered enough, or it overwatered them. I would say that the lawn and plants are much healthier now and the Rachio system does water only when it is needed. It does what it's supposed to do – it adapts to the changing weather conditions! That is savings right there. Additionally, our local water conservation organization puts out a “weekly watering number” (amount of water in inches recommended for watering based on weather forecasts.) My Rachio has fairly consistently used about ½ to 2/3 of their recommended amount, yet things are still thriving. So, I know I'm saving some water.