@Quincy The micro-climate issue can certainly be a factor if you don't have a good PWS, depending on where you live. I'm in a desert climate, so the rain issue is of little consequence. The big factor for me is the quick rise and fall that we have in temperature extremes, and Flex Daily certainly seems to handle that well, even with using the airport's station 15 miles away. It may be 110F there but 113F here, so no big deal. If I lived elsewhere that had more precipitation then I'd be looking much more seriously at a PWS to make things better for the reason that you noted.
The infiltration rate and saturation (available water) issues you mentioned are minimized by getting someone to do a good soil analysis for you. Apparently in places like Boulder the city does it for free. Here, it would cost me ~$75. The data can be put into your zone settings so that the algorithm can get you closer, but of course it won't be spot-on since it's still an open-loop system. The end-all here seems to be a good soil moisture sensor, or set of them, connected to the controller to give you a closed-loop system. The technical challenge is building good, reliable & durable wireless moisture sensors that won't need a battery change every month, constantly drop connections, or get destroyed by a lawn mower or weed whacker. I imagine that might take a while, but I would think that the Rachio guys would be on it as that market develops. At least I hope so.
Thanks for sharing great, constructive comments, and good luck with the rest of your investigation!