i love looking at midpoints....
esp. when i look at synasty charts... i find they're way more revealing than both synastry and composite.there isn't a lot of stuff on line, but when i look through them i don't really need to look anything up because it hits so close to home that it's hard not to understand the energies.
i usually guess them before i look anything up as well....
i'd say they're very impt.
edit: oops i just re read your question...yeah i don't think i can explain the mechanics behind it or how why it works...i just know i like looking at them.