I have never used or seen an AS/400. I remember that during the late 1980s and early 1990s I worked with some people who used one. After I left that job, I encountered one in a Metro station; she told me that her section had switched to an NT based solution, which was much cheaper but also much more prone to failure. And I did know a guy running an AS/400 perhaps 15 years back. He was very happy with it.