The big thing that the Amiga had and in a way still has over any windowz OS is that it can multi-task very smoothly and effectively. Yes modern day windowz machines have more raw horsepower but they need it to do multi-tasking as well as they do. Another member on here memtioned this in another thread but I have also done this, on the Amiga you can format more then one drive/partition at the same time. Try doing that on a PC. :-D
The Mac OS has done well in this department and is leaps ahead of the PC in this regards.