I've bought this shirt and the 1MX Modern Fit (which is slimmer fit). This shirt fits like a regular business shirt, but gives more of a tailored fit. I'm a skinny guy (5'10, 135lbs) and the size small looks perfect on me.
These shirts have the traditional business shirt look, but the colors and slimmer cut gives it a stylish look. This is def a shirt for those of you who like to have room to breath and don't necessarily want the skinny fit (Modern Fit).
It does not give as much poof at the waist as normal business shirts, but it does have some. Nonetheless, it's still great.
I'd recommend these shirts above the Modern Fit if you want a shirt that is versatile. These shirts look better untucked than the Modern Fit does.