[phantomread]

Biggest issue I can think of is trying to do PWM _and_ WiFi work simultaneously on an esp8266. If you have, say, an esp8266 serving up a small webpage for control and don't want to add an external PWM board then you might notice intermittent issues. This is more obvious if you're controlling something like a lighting ballast that's PWM controlled.

Of course now that I'm looking around I see https://github.com/khoih-prog/ESP8266_PWM which seems promising (subdivides the second of two available hardware timers to allow PWM that isn't sensitive to other running code). So there's multiple workarounds (libraries, breakout boards) besides upgrading to an esp32.