This section should only be used to convey relevant information not addressed elsewhere in your application. This may include an explanation of employment gaps, academic aberrations, supplemental coursework, etc. You are encouraged to use bullet points where appropriate.
The optional essay and our stance on it has changed over the years (for more on that, read this). Years ago we’d say to do it always-no-matter-what. Then schools seemed to make a POINT of not wanting stuff they didn’t specifically ask for. And now, given the trend toward shorter and more targeted applications, it can go either way.
Generally, if a school gives you a berth, take it. Haas is giving you that berth here, so, if you have something to say that hasn’t been covered elsewhere, say it. (If you’re working with a solid admissions consultant, you may want to run it by him/her to get a seasoned opinion.)
For those whose quantitative abilities may be questionable, either through a not-mind-blowing GMAT score, or through a career arc where those abilities aren’t necessarily evident, this is an excellent space to make a great case for yourself.
But even beyond that, the best way to approach this is to consider all the dimensions which give your candidacy real MIGHT, and differentiation power against the competition. Then review what stuff you’ve covered in your other essays, and where there are HOLES, it MAY be something you can address here. It tends to be less helpful when you double-up on a trait, with presumably a not-as-good-story-as-the-one-you’ve-already-told-elsewhere. A “second” impact story, for example. It’s more powerful if you’ve come across as the Indian IT tech guy with mad quant skills, but you also have this insane depth of experience with volunteer/community work that looks completely different from the typical MBA applicant. This could be a place to explore that. Or if you’re Chinese with an interest in finance, is there some aspect to your international travels that makes you seem utterly different from your demographic? This could be a spot to explore that.
Whatever you do, don’t play defense here and say stuff just to say stuff. More like: imagine a blank canvas and a shot to say EVERYTHING AWESOME you need to say; imagine it’s FIVE things, and you’ve been able to cover THREE of them in the other essays. Great, pick one of the two things you haven’t covered (whichever promotes your multi-dimensionality the MOST), and dig in right here.
Whatever you do, this is NOT the place to meander and be verbose. The optional essay is all about extreme efficiency, and matter-of-fact-ness.