I'd never considered the break angle over the nut before... What do you guys perceive is the advantage of a more extreme break angle over the nut? I'd actually think less is better as you don't want strings binding on the nut during tuning.
The down angle behind the nut can affect quite a bit. Binding is probably not an issue much with bone and a properly sized slot. For a .036" string, you'd use the .042 file, give it a little room (warning, this is from memory).
The down angle affects playability or "bounce" in the nut area, the cowboy chord area, among other things probably.
Early Gibson guitars had pronounced headstock pitch, 17º. Gradually, through the Norlin era the angle got shallower and shallower to prevent breakage (also added a nice volute ;-) until the headstock was virtually flat like a Fender. This really killed the playability up by the nut (and the tone), the guitars just don't have the same feel, it's harder to get your fingers under the strings perhaps.
Same thing with down angle at the bridge/tailpiece on a Les Paul/SG/335 stop tailpiece stye guitars.
If you slam the tailpiece to the body, you get the greatest amount of resonance, sustain, and also the best playability. Most rock stars seem to like to screw the tailpiece right down to the wood, I aways do. But others like to do that and then wrap the string around over the top of the tailpiece, lowering the tension by raising the break angle for a mushier feel.
Down angle at the ends of strings seems to be a really important thing.
I think you have the right amount of wrap on a Guild style guitar (pitched headstock) when the strings are perfectly perpendicular to the headstock face. Often times, you need extra wraps on the shortest strings to achieve that angle.
The Eric Johnson Strat actually has tuners that get short as you get farther from the nut so as to not need a string tree.
It's a science into itself, like every other part of the guitar ;-)