After a bit of a struggle, I've installed several of these devices, and they are all one could hope for. I'm using them to replace Insteon devices, which worked most of the time. The Shellys are fast and reliable - They are a night and day improvement.
I am very grateful to Aaron and Joe (whom I believe are responsible for the relevant plug-ins) and the others who helped me figure out how to integrated them into Indigo.
If anyone is interested in my documentation, PM me.
Bob