When I'm working/playing with an old system or emulator, the first things that I 
want to understand are the available input and output methods. I want to know how 
I can interact with the system. The other capabilities of the system are secondary 
to input/output in my mind, because without input/output all the power in the 
world would mean nothing.

Take the universal example of Helen Keller. Limited input/output compared to most 
humans, but still a viable method (touch) and patient teachers that allowed her to 
interact with the world in a very meaningful way. In the Arizona Science Center 
once they had a display on computer control via eye-movement tracking. The user 
could simply look at the screen and type or play games, all using eye tracking. No 
other input/output was necessary beyond the eye. That, of course, is currently 
available technology, other more experimental technologies are likely in the 
works, with the shared goal of expanding input/output for those with impairments.

It's interesting to me that there is such a strong connection between technology 
and the human experience. I suppose if you consider technology as an extension of 
that experience, created by us and for us, then it makes sense. But it's still 
interesting to consider.