I used it to control a 220V SPA blower + 2 independent lights- with a channel to spare.
I'm not a fan of their wiring diagrams but after a bit of studying you can get a clear picture of what you can do, and figure how to maximize your channel usage.
I have the pro model, and the AC INPUT is used to power the unit. There is NO need for a DC input.
I was impressed with its response time when toggling the on/off. The app vibrates your device for a nice tactile feedback to confirm your command.
Pairing was pretty simple. It uses the 2.4Ghz band( obviously better for range).
I would pay a few $ more to have more robust connectors. I have 12AWG connected and they are a tad too stiff for the connectors. Will likely switch to stranded where I can. I've installed it in an ABS outdoor weather proof box.
App is nice and user intuitive, everything worked for me after a painless pairing process.
If I experience signal issues, I plan to add an external wifi antenna to it....

Do you have Sonoff 4Ch pro R2 Wi-fi Smart switch? I used to use R2, and it works well.
Pro R3 is hard to connect with phone. if you have it, I would like to exchange.
Thanks
Tracy

Unable to connect to home network. Will update rating when I hear back from manufacturer.
It took about 2 days but I did hear back from the manufacturer with detailed instruction on pairing.
The unit was paired and worked right away, I was up and running in a couple of minutes.
Good customer service; however, I would have appreciated better instructions from the get go. Kyle (at CS) promised to forward my suggestions to proper channels. Four stars

I have a very small one circuit sprinkler system that I wanted to control. The Sonoff 4Ch Pro was the answer for me.

I just flashed ESP Home on the Sonoff and was up and running in 30 minutes. The only problem I had was I lost the ability to have the 4Ch Pro act as an RF bridge. It can send out RF control signals to specific devices, but it can't be a general purpose hub for RF that bridges to MQTT over wifi. Not a big deal for me, but its a loss of capabilities. I figure its a good trade off to get 100% local control with no spyware or information leakage outside of my home.

I am puzzled by the mixed reviews. I installed 2 of the R2 units for my first stab at home (actually RV) automation. Everything went as planned, with no issues with connectivity, wifi signal, interfacing with Alexa Dot, etc. I am not sure if I just got lucky, or if others are not following the available instructional videos which are all over YouTube. I will say I planned out the system before the installation and re-watched the best videos on the Sonoff 4 channel controllers. I am going to expand my system and purchase 2 more units as I am very excited about the automation success. I will also add, in Google Play, the ratings for the eWeLink app also left me concerned, but again, everything works as it should and the app is very user friendly. I am not aware of any security concerns or having the system "open" as others have mentioned. In fact, if there is any complaint it would be I have to log into the system again with user and password everytime I use a different device to control the board (sans Alexa). I control lights, generator, and an awning with my first two units. Once I connected my Echo Dot, it doubled my satisfaction as I never thought it would be so easy to speak out commands. It really is like having a personal assistant at your immediate disposal to do tasks and research for you. There will be no going back. And for those of you considering marriage, you may want to consider this instead. Far cheaper, hasn't talked back or complained once, and if it ever misbehaves, you can easily pull the plug.