Here's a short experience summary of my move from a Rain Bird ESP-SMT to the Rachio Gen 2:
I have roughly half an acre to irrigate using 13 zones. Location: Southern California, Inland Empire (Rancho Cucamonga).
I had the Rain Bird system installed in September 2011. The guy who did the install was a consummate professional. He did catch cup tests, he tested root depths, he understood my crops. Water usage promptly dropped and all was good.
Over time, things were mostly fine but the system began to get a bit creaky, the sensor pod clearly needed some recalibration, and most unfortunately, my installer's company went out of business as he was unable to compete with very cheap, unlicensed, uninsured competition.
At the beginning of May this year (2017), I came across Rachio. After a bunch of research, I ordered one. It took about an hour to do the physical instal, including the wifi connections, etc.
Working with the web-based app, which I think is best for wholesale mods, it took about two hours to enter all the configuration info going straight from the ESP SMT profile zone-to-zone. It would have been faster, but I had to map the RB nomenclature to the Rachio nomenclature in some cases and it wan't completely obvious. I'm using a single Flex-Daily schedule.
I've had my own PWS for 7 or 8 years connected to WU. It uses a Meteo Bridge to connect to the Internet so it was trivial to add both CWOP and PWS and I now get the added advantage of having the MADIS & Gladstone checking of my station's accuracy.
Being a data nut, I've kept daily minutes-per-zone-per-day info since my RB install along with all tweaks I had to do to meet our progressively more draconian drought restriction rules. So, I am able to compare my Rachio zone runs to the RB runs on similar dates.
Admittedly, I've only been running the Rachio for a bit over a month, but so far it is performing, as far as I can tell, much better than the RB solution. Irrigation tends to be for a longer period for a zone (maybe with multiple cycles which the RB was supposed to do but wasn't very good in practice) but the frequency is less and the grass, etc looks better (subjective, I know, but I think so).
All in all, the Rachio is a super winner IMHO. Please don't get bought and absorbed by a bigger player who wants the installed base But if you do, make sure all the founders and early employees make out big -- you deserve it!