I see so many posts saying go to Tasmoto I thought I would come and ask who has given this a go?
Which devices can be flashed and what functionality is gained or lost?
Sure I also read you need to have a server running in the house as well, is that right?
It all sounds very involved, was it worth it for you?
I have Tasmota flashed on one of my sonoffs and you loose control via the app. You won't be able to have your sonoff connected to the eWelink app anymore, only locally via the device's webpage or together with another system like Domoticz.
Yes, you can use eWeLink any longer after flashing Tasmota. But you can use a local automation hub (Domoticz, openHAB, Home Assistant). You can also control it with the Amazon app and many other MQTT apps like Yeti or Yonomi. Many of these also still give you the ability to control the device remotely which away from home. Replacing the firmware just opens up a great deal more options and automation features.
I personally did not have a good experience with Tasmota firmware. My devices got bricked if I ever tried to upgrade the firmware. I tried this on 5 different sonoff basic switches. I have been using the stock firmware.
If you're wanting to move to Tasmota because of Home Assistant, there is a project available on GitHub that you should look into
5 million Tasmota downloads... OTA works perfectly for the vast majority of these users. There was an issue with 6.7 that was repaired w/in 24 hours. Other than that, when a user's OTA update fails, my experience has been 999/1000 times that it's a user error.
Perhaps there is some misconfiguration on your part?