chaoticsilence
Would love to hear how the rest of you approached this aspect in your letters.
Look at it this way - when you write a cover letter for a job, you don't talk about why the firm is a good fit for you - the firm doesn't give a sh** about that. Instead, you talk about why YOU are a good fit for the firm.
Do the same for Sloan - do your research to figure out what are the THREE cardinal things that Sloan holds as UNIQUELY emblematic of its mission. Fewer than three is sloppy research; more than three and you won't be able to do justice to your cover letter.
In the letter, you then say, "I'm a good fit for Sloan because I value what Sloan values - A, B, and C. Here are relevant examples to support my statement - bam, bam, bam. And oh, you guys also really value leadership and taking initiative. Why, so do I! Here's another example - [insert leadership/initiative example, as asked by Sloan]."
I hope this makes sense. Basically, stay relevant to Sloan, not to any generic business school. A summary of your past achievements, whether you do two or do fifteen, is useless if they're all to do with touchy-feely marketing stuff - Sloan doesn't care for touchy-feely; Kellogg and Haas love that sort of stuff. Similarly, Sloan doesn't care if you walked twelve miles uphill each way to school when you were a kid, and that it taught you to struggle in the face of adversity - they ONLY want recent examples from your life. Choose achievements and experiences that align with Sloan's core values.
And you're done!