Plummet said..
Going from beginner to intermediate I think would be when you have mastered upwind, water starts, solo launch/land, easily land a basic jump. When you can do all those things without consciously thinking how to do them.
From intermediate to advanced gets a bit tricky. There are so many different disciplines that you could be a master of one and be a novice at the other.
Reakon plummets on the money here,
my 2 cents worth,
I would say the discipline could be segregated further,
Weather forecasts knowledge, do you know where and when to go for the best conditions for your area, Every notice that the same dudes are out when you find a spot thats cranking....... they know
Set up efficiency and gear knowledge as some people rip on the water but take forever to set up and spend as much time on the land as they do in the water, have seen a few dudes fumble their way through setting up lines launching then landing awkwardly being a jerk in launch areas and then when their out on the water they tear the bag, getting the most out of your kite line set up trimming ect.
Self rescue experience for those that have had to do it, experience outweighs knowledge hands down, how much real experience have you had?
theres heaps more but you get my train of thought