The older systems ran a flavor of UNIX called Ultrix. Thus AXIS and the users of AXIS became a testing ground. This was very successful. The good news was that it was pretty much a non-event. Though we announced it in the message of the day and newsgroups, I think most people didn't notice the announcements or the change.
Many people still use AXIS because they believe that it is the faster of the two systems.
As the load on MHC increases, it might become true again. AXIS has also taken on the role of intranet server in order to serve files and other information to sources on-campus only. AXIS cannot be reached directly from off campus.