Agreed, awesome chips. Another neat option you can get in us or for a third the price from China, is the witty cloud board. Comes with esp, light sensor, and led, button, and removable USB programmer board. Plus USB power. For about $3.
I've used them for kids lights, a chicken coop door controller, remote temperature monitor, and garage door controller. It's nice as a software person to be able to control and monitor real world things exactly how I'd like too.
You can get bare esp8266 boards from aliexpress for ~$1.20 per unit shipped from china. You'll have to solder slightly more, but if you're building things with these, this is the way to go.
I did my prototyping on the much nicer (more features added out of the box) esp8266 Huzzah from adafruit. Once I got the code and everything working, I bought a bunch of the cheap ones + the sensors and then went to town. You can manage a fleet of them with the mongoose os stack https://mongoose-os.com/ (note that the fleet management of 40+ sensors is a paid service, but all of the libs otherwise are free and oss).
I've used them for kids lights, a chicken coop door controller, remote temperature monitor, and garage door controller. It's nice as a software person to be able to control and monitor real world things exactly how I'd like too.