We went full in and not only open sourced the firmware of our air quality monitors but made it completely open source hardware, this means it includes the electronic schematics, enclosure files etc. [1]
I believe it was the single most important decision we took as a company and probably also contributed to a large part to the growth and success we are having now. It enables us to build a really strong community, and also differentiate ourselves clearly from other manufacturers that are all pretty much only offering proprietary solutions.
But I think people need to be aware that by open sourcing, they put the company on a different trajectory. For example you are basically making yourself a lot less attractive for VCs.
When I see how much other companies can get investments that help them grow faster and make more impact is the only times when I sometimes wonder if other models might have been a better option?