I work at the Toronto international airport control tower and we use Amigas basically for everything that involves getting the planes safely up or down. Frankly speaking, I don't think that PCs would ever be up for such a responsible and demanding job. They have been running reliably for the past 20 years since we originally implemented the "Amiga in the workplace" solution.
We are still using mostly Amiga 2000 units with 2.0 roms and are hoping to upgrade to 3.1 roms/OS3.9 some day, however our development department is still reluctant to recommend and push a safe migration, as software compatibility might pose a problem. After all, it is an airport and all systems must be 100% funtional, all the time.
We are constantly upgrading the workplace with new units, and for parts and systems we mostly go to eBay.
It's a wonderful place to work at! I wouldn't trade my job for anything in the world.