Jonwrote a review of Patagonia Slingshot Down Vest - Men's on January 15, 2013
Familiarity: I returned this product before using it
Ordered both a Large and Medium to see which one would fit me - neither came close. I'm somewhat thin (but not overly so) at 6'3" and 185 lbs.
First tried the Large - I could seriously gain 40 pounds and still have plenty of room to fit in it. Next tried the Medium - really tight on me, not to mention short as well. Also did not care for way the neck looked when zipped up.
My other Patagonia clothes (R1 Hoody for example) I've always ordered in a Large and it fits me perfect. The Patagonia Down Sweater Vest also fits me fairly well in Large.
Other than that, I think this vest has a great style, was very lightweight and packable, and I loved both the front pockets and side hand pockets. If you're able to try one on first, it may be great for you.