I appreciate the AmigaOS because it has an overall feeling of high technical quality. It's lean and zippy, and it makes you feel in control of the computer rather than under control of the OS. When comparing the AmigaOS to Windows on a modern computer this becomes more transparent - but I still appreciate it being there, knowing that it's all done with a fraction of the resources compared to the Windows equivalent.
From a programmer's point of view I feel that the Kickstart APIs are horrible. The documentation leaves much to desire and there's just no comparing it to the MSDN. I believe there were too many cooks involved, each and one following their own recipe.
There has always been a gray and sterile feeling looming over the PC and Windows, and there's little fun in using and programming it. The Amiga and its OS on other hand feels very genuine, and I will always appreciate that. However, I will never switch from Windows to AmigaOS for everyday use because in the end the Windows alternative is just more comfortable and easy to use.