I suppose it depends on the experience of the people you're showing it to. I've not had any difficulty explaining, or people grasping the rules, myself. Demo games were run for thousands of people at many events, and the response is not generally one of confusion.
I don't think the rules themselves are complex. As you say, the variety in possibilities from the many different units gives you a lot of things to consider, but only if you start with everything on the table (metaphorically or literally) at once.
When I'm teaching people, I start with just the core box. That's got loads of replay and depth without anything else. Then simply add extra stuff at the pace your group is comfortable with.