Easiest way to look at it is that each different flight number counts as a segment. For example, say that AA has two flights from lax to nyc. Both connect through dfw, and are effectively the same flight, but at different times. One has a single number, while the other has two different numbers. OWE will look at the first combo as one segment and will look at the second combo as two. The fact about some of the smaller places is a disadvantage. One quirky thing is about Aruba. AA flies from SJU to AUA, if I remember correctly. Of course SJU is in North America, but Aruba is considered South America. If you want to go there, you need to add on the S/A continent, and can't go anywhere else in it because you have to cross back into N/a to go anywhere else. Go figure.

Intercontinental flights are not segments. They are interconental flights. Each circumstance has its own rules, so look at Hsi's site for your combo.

If you work it right, the lack of milage restrictions is nice. But the rules make the entire thing a pain in the arse to figure out.