I have the OXO good grip 4-sided box grater.
I use it for harder cheeses and root veggies. I slice "up and down". I like the large, non-slip handle and the non-slip bottom, since I apply a fair amount of force.
I notice I don't really use the smaller sides that much (too small).
I also notice that I seldom scrape the food all the way to the bottom of the grater. If I use the attached box, it lifts the grater up and I'm likely to use the entire surface in my stroke (more efficient since I'm using the entire surface). However, the plastic box slants inwards slightly and destabilizes the grater (eg - it slips on the counter - ouch!). Without the box attached, it is very sturdy and stable.
If the attached box was more stable (a different shape?) it would be a more efficient design. (Also, I find the capacity of the box is often too small).
You're the designer, so wouldn't it be neat if a box grater could be hinged in some way, opening up for cleaning (or storage) without affecting the sturdiness when it was "snapped together" when you were grating on it?
Also, maybe a different shape would be interesting to explore (?3-sided? ?5-sided? - there's 6-sided box grater on Amazon but I've only used the more usual 4 sided ones).
Think out of the "box"