Measure angle of drop in NL2?
Basic trig.
First off, display your radius comb - this will allow you to find the "inflection point", i.e. the steepest point on your drop. It's best if your vertices are closely spaced, such as...

Focus on the two vertices on either side of the inflection point. What we want to do here is get our set of coords.

Let's get our hypotenuse of the first triangle - marked out with the red line here. Get the difference between your X coords and your Z coords.

In my case, my ΔX is -0.3386 and my ΔZ is -0.1659. We can use Pythagoras' theorem to get the hypotenuse of this triangle.
(0.3386^2 + (-0.1659)^2)^0.5 = 0.377058046. This will be the base length of our second triangle.
We now want to get our ΔY. In my case, it's -0.33.
We can use TanΘ = opp/adj to get our angle of descent.

We can therefore calculate, using our value retrieved, our arctan value - which is equal to the angle of descent.
atan(-0.33/0.377058046) = Θ = -41.1922841, which is the angle of descent in this example.
To simplify the formula:
atan(ΔY / (ΔX^2+ΔZ^2)^0.5) = drop angle
There are other methods using the API and scripting, however for more rudimentary guesstimates, using trig and Pythagoras would get you a good enough result for what you're looking for.
Or bring out a protractor and throw it on your screen. Not as accurate and your screen probably will break, but it might save your calculator some battery.
(seriously though, very nice tutorial :) )

I've seen people present the angle of their coaster's drop on YouTube. Does anyone know a simple way to measure how steep a drop is?