MICROCONTROLLERS

Hmm. ESP32 boards are typically $5, though $18 is still cheap in the great scheme of things, there's a huge price differential here.

It seems like the big selling point will be Arduino IoT Cloud ? ("Available August" ??)

In general, I remember ESP32 using a lot more power than a typical uC, that WiFi / Bluetooth radio is pretty expensive. And it also takes a long time for WiFi radios to connect and talk (finding access points, connecting, spinning up TCP handshake, etc. etc.). The IoT preferred radio historically has been Zigbee for a reason, though harder to setup it really cuts down on needless chatter and lowers the overall power-consumption per radio-message.

That being said, WiFi is damn near universal and one of the easiest ways to do things.