Regarding whether IxD is limited to systems which have a software
component. I disagree, I mean people do interact with objects/systems in
the real world which don't have any software components, I think any
system that interacts with people can be worked upon/improved. It's true
the field of Interaction Design evolved out of the need to improve
software systems, but look at something like the telephone. Most
telephones now have software (somewhere down the line), we can apply
interaction design to telephone systems at various levels.
But designers have been doing this for years, AT&T worked on the design
of the telephone improved interaction several times. Even back when it
was all hard wired. So it has been going around for a long time, we just
named it recently.
I think Interaction design has applications in every field, think of
pop-up books, that's interaction design. Product designers have been
doing it for years.