Earlier quoted context omitted.
As a parent whos been buying various blocks over the last decade I think the main advantage lego has is the level of quality. When the characters we wanted were with other companies I would maybe buy a few but they never stuck together quite right, or would break too easily. So I wouldnt buy more, or if i did it was just the character and not the set.
Absolutely. We have a bunch of Megabloks mixed in with our Legos and I can separate them even without looking. The difference in tolerances is pretty interesting.
I seem to recall a post on the front page of HN discussing the incredible tolerances they achieve, at an almost unthinkable scale.
You can buy Lego blocks anywhere in the world, and they click perfectly with Lego blocks purchased anywhere else in the world, and purchased at just about any time in the past or present.