I have a few of their boards and my experience with them could have been a lot better.

Their documentation is rather poor. Parameters to function/constructors are often left out, leaving you to go through the source to figure out how stuff works.

The standard modules can have different functions/variables between different boards. It makes sense since some boards have capabilities others don't. However there is no documentation on this.

Finally, in my opinion, some of the adafruit_* libraries are not well designed. There are many "kitchen sink" libraries that try to do everything. I also noticed that while they do appear to use pylint to enforce good standards, almost all source files have at least one check disabled...